What I've seen in my lengthy career of counseling is that IF a woman is pregnant and either has a miscarriage or an abortion, she's likely to continue experiencing confusing and contradictory effects of from her pregnancy-altered hormones for the duration of the pregnancy. And THAT affects how she thinks&feels (they're ALWAYS inextricably linked, can't think w/o feeling & usually also can't feel w/o having feeling-colored thoughts). And IF she's able to remember some vivid thought/feelings from that period, she will be capable of regret AND able to apply rational counterargumentsto those regrets (including those colored by the relief & excitement/pride&joy attached to what she has done INSTEAD of raising or giving up a child at that time) for many years, depending on how often she chooses--or is accidentally reminded--to remember.
And I agree with everything Rev.Dr. has written, minus the apparently negative judgment about your partner. Youngish men are usually so unaware of themselves and their emotions & effects on their GF that they don't realize what their doing and its potential future effects. I think you can assert yourself for a more responsible approach to birth control, without going to a counselor--unless you haven't developed that assertiveness in your romantic relationships yet. In that case YES, go to counseling alone or with him, or talk to an older woman who is more assertive in love relationships than you are. The differences in young people's assertiveness are very impactful in romantic relationships(men naively doing&saying what their emotional-thinking tells them vs women naively being submissive to please and avoid disappointing anybody whose love they live on like emotional food) and it does take considerable training and experience for them to develop awareness they don't yet have.
I would also add, that I wouldn't want you to choose life-long coparentship with your boyfriend on the basis of an accident, because the quality & quantity of that coparentship ALSO has an unavoidable effect on the child if there is one, unless you marry somebody else within a year, and make sure the biological father can have nothing but a beneficial effect--and that's not entirely in your power. A lot of young people put their first supposedly enduring partnership at severe risk by committing to it before a year of premarital testing has passed. And it can take as long as a year for the most difficult-to-live-with differences and problems arise in a love relationship. And if you keep escalating the highly emotional stages of your relationship (such as getting engaged, coping with parental disapproval--aka Romeo&Juliet-Effect, pregnancy, childbirth, getting deployed to Afghanistan, etc.) you'll never get a chance to discover what's likely to present very difficult problems between you as your years together mount up. In fact the most likely times for divorce in cultures world-wide that permit divorce without huge struggles are YEARS 2, 3 and 4 since the beginning of the romantic relationship, because the biologically-induced PASSION simmers down by year 3, and interpersonal structures for managing differences and conflicts have not been developed, because nobody wants to worry about them when the LOVE IS SO GREAT.
I'm taking responsibility for an admittedly biased advice to you (using "I wouldn't want") because I realize that abortion vs accidental birth is a very emotionally charged topic for anybody who's ever had a close brush with those issues. Both the RevDr and I (Dr.LicMarriage&FamTherapist) are preaching to you, because the issue matters a lot to us (tho I'm presuming knowledge of her that I don't have--so I apologize for that). That also implies that you'll get strongly emotion-colored responses from almost everyone you talk to, even if a counselor is trying to appear completely neutral. In fact, I don't think complete neutrality is morally defensible for a licensed counselor, because one must consider the lifelong issues that are statistically likely for the unborn child, even though lots of church-related counselors may ignore them when they counsel that abortion is a sin and a crime.
Since you're an atheist, you might have your own bruises from religious influences in your family of origin or your present life.
I hope my imbedding of abortion-regrets in the physiological context of a woman's bodily experience helps you to perceive your emotion-colored thoughts ALSO from a more "objective" (that is, NOT just immersed in the colored-fluid of emotions) standpoint. Feel free to respond to either me or RevDrAbbot, and it's your choice only who you decide to pay when you release your deposit. Perhaps making that choice will exercise your courage muscles (French for "heart-stuff") for disappointing another person because you choose one path and not another. Life is full of such choices, and dodging them because you don't like the guilty feelings that you have when you consider choosing only postpones the time in your life when you're strong enough to stop hoping to please everybody.
Sorry I preach so much. But I've had 40 yrs experience in therapy, and I'd rather pour more into your teachable moment if you're mentioning it at all. I'm keeping track of what I've learned when I write this way, because it matters to me, but it's none of my business to insist it should matter to you--except as a fulfillment of the Hippocratic Oath (First Do no Harm) extended into expressing concern and forewarning about potential future harm as the responsibility that goes with the expanded knowledge involved in both individual and marriage & family therapy.
I have not suggested that you should break up with your boyfriend, but that you need to tell him he must join with you in preventing a pregnancy. I've suggested that perhaps you don't know how to say clearly what you will and will not do with him, because you were never allowed to do that when you were growing up, and that you need to not fear disappointing him if you refuse to have sex unless you are protected from conceiving a child. You say you don't want to break up, and that might mean you think that if you tell him you must have protection against pregnancy he will not like that and might leave you. Is that what you think? If thoughts like that keep you from asserting yourself, then you need to talk to other women who DO make sure they won't get pregnant with their boyfriends, or you need to have a session with a licensed counselor who can teach you how to stand up for yourself. If you have had many boyfriends in the past who were assholes, then you definitely need to learn how to stand up for yourself, because that will send the assholes away, and only a man who can compromise and care about what you want will stay with you.
Women who find themselves with assholes often have usually been raised with a messed-up father or brother(s), so they've never learned that they don't have to just struggle to survive in a situation that's not pleasant or even always safe. It's not your fault if you did have mean or messed-up parents (or father & then similar boyfriends). But it takes a lot of personal change for you to make sure you can make this or your next boyfriend be even better with you than he has been so far.
If you learn how to stand up and speak out for what you need (protection from accidental pregnancy) with this BF, then either he will understand you and want to protect you and himself from an accidental baby, or he won't accept your need for control over your body and WHEN you are ready for motherhood (my wife was 37 when we got pregnant, my mother was 45 when she had me). If he won't respect your need, then you may have to get another BF, but then you will know how to talk to the next guy so that you don't have sex without being safe. And if you're not 40 yet, then you don't have to be scared you'll never have a child.