Hi, I'd like to help you with your question.
It sounds like you have strong feelings for this woman. It is common to feel strongly about a new love. They are on your mind all the time, sleep is difficult and appetite goes down. Weight loss is common. You feel infatuated. This feeling usually lasts the first few months at least until the relationship has more time to develop.
What you don't want to have happen is you become unnaturally obsessed with her. Obsession is a fine line from infatuation but you know you have crossed it when your work suffers, you cannot accomplish tasks, you send her unwanted gifts, you are jealous and try to restrict her freedom. You take time to find out where she is through seeking her out or calling her all day.
If you feel obsessed, then it could be an indication that you have a problem. When you cross boundaries and cannot step back, then seeking help is important. You do not want to ruin your relationship over this. Talk with your doctor about a referral to a therapist. Or you can search on line at http://therapists.psychologytoday.com/rms/.
If you think this is not an obsession, then you may want to look at why this woman is important to you. Does she fulfill a need that you have? Do you feel something is missing you in life? When you find out what you feel this woman fulfills for you, then you can begin to work on fixing the problem. You may need to talk to someone to get input on this. It is often hard to see our own issues without help.
Once you can pinpoint the answer, you should be able to resolve this quickly.
Let me know if I can help any further,
It sounds like you are doing a good job in trying to address the problem so it does not turn into an obsession. But since you have experienced this problem before in other relationships, then therapy might be a good option for you. Getting to the root of this issue is important so you can keep this relationship going. Otherwise, this will continue to be a battle for you.
There is nothing wrong with therapy and it concerns me that you feel your girlfriend would have an issue with you appearing weak. It is actually a sign of strength to seek treatment. You would not hesitate to see a doctor for an illness, why would this be anything different? If you think of it that way, it may help. Also, therapy can help you be stronger and have a healthier relationship something both of you want.
It may be a good idea to see someone she does not know so you can discuss this problem fully without holding back. Her friend should not see you anyway due to a conflict of interest (therapists are not supposed to see family or friends in therapy). Try your local community mental health center if you are concerned about cost. They can see you on a sliding fee scale.