-- Let's put this in perspective just by the definition of "love" ok? Love is a partnership of two people (especially with a child) to stand together not just when it's easy, but to stand stronger together when it's hard.
Love puts aside petty jealousies and is built on a foundation of trust that never has reason to waiver. Love is putting that child ahead of your own wants and needs because she is the future and you will sacrifice whatever you must in order for her future to be better than your present. She will learn at your knee and at your elbow how to raise her children to be even better than she is.
--- Love is not leaving. Love does not waiver and love does not question whether or not it is love.
You are not describing love when you describe this relationship. What you do describe is a "habit", a sort of addiction.
Yes, it is possible and even common for people to end up staying, leaving, returning and doing this pattern over and over out of addiction (or habit).
Breaking this habit is absolutely necessary - and only then can you (both) start from a healthy base and decide whether or not this is a relationship with true love in it.
Breaking a habit like this is harder than getting off cigarettes or drugs in many cases. You will need help to get through it - and there's no doubt about that ok?
You have to find a counselor in your area to get you going and to help you not only find the strength, but the tools to use to make the right choices and implement them.
Just 4 sessions to start - that's not too much to invest in your life, your future and your baby right?
--- Call the local mental health center of your hospitals to get started. They should be able to give you options that will work with your own circumstances, both personal and financial or insurances.
Also consider local churches - even synagogues for 'all faith' counseling. Many times it doesn't matter if you're a member of the congregation or not.
It's obvious that you are anguishing over this up and down, in and out, on and off situation. It's not the stability you and your child need and deserve.
What matters is that you've recognized it and with that, I trust that now that you realize what is going on, you'll not hesitate a single day to take the next step.
You're smart - keep trusting those instincts