Well, it sounds to me like you are in the "Q" part of the LGBTIQ spectrum ("questioning"). There are two points that I immediately keyed into: 1. You say you feel there is something holding you back. 2. You feel the need to transition in some way, but don't know what form you need to transition into.
That being said, take it slow and explore your options. Try on different gender identities (or non-identities) and see what feels most normal. Remember that there are a lot of options between boy and girl, between masculine and feminine. Try to imagine what your life would be like if you actually DID physically transition...and not just the good side; think about the drawbacks as well. If you feel not-boy but also not-girl, think about how you would define yourself if you could invent a completely new gender.
Most importantly,if you can, find a counselor or therapist who is experienced with gender issues and talk about all these thoughts with him/her. Their entire job is to help you sort through your confusion and figure out who and what is the "true you" and then to help you become the best "true you" that you can be. Maybe that will mean physical transition, maybe it will mean adopting a "non-op" identity of some sort, maybe you will find that you are already your true self and just had a lot of psychological baggage to work through.
Whatever comes of it all, know that you have friends here who will accept you for who and what you are and will listen non-judgementally.