I don't believe you're going crazy, but I do believe that you may have a poor self-concept that probably has it's roots in childhood. Are you in therapy? Also, Akua is right... if you've got a great guy that wants to marry you don't run away from love. Communication is one of the most important layers in the foundation of any relationship. It may help to strengthen your relationship if you shared what you've been going through. If you can't do it in private, then a marriage counselor would be able to help you to express yourself. But I do suggest one-on-one therapy for yourself if you haven't sought it out yet. I've been in therapy for only 5 months and so much light has been shed on my situation. It will help you too.

Best wishes