I'm really glad you've reached out here for some support - coming from a small town and having repressed your "queerness" for so long would make this time of your life, as you expand and explore your feelings and identity, both exciting and frightening.
MaxineC made a beautiful point that you can celebrate your courage in leaving your repression behind and starting on your journey of discovery.
Rest assured that there are many people out there who have very similar feelings and experiences to you, so please do not feel like you are strange in any way. Are you still in the small town you grew up in, or are you closer to a city now? Metro areas can be a lot more liberating when exploring this kind of thing.
My partner (female) had perhaps similar feelings and experiences to you, and her way of exploring it all included this sort of "boi" identity for a time during her twenties. I don't know if this is something you could maybe relate to.
There are so many ways you can express yourself and explore who you are ... and it's ok to not know "who am i" yet ... explore, experience, have fun.
Do you think it would help to be open with your girlfriend and say something like "hey, I know I'm awkward, I dunno what I'm doing, but I really like you, I just get nervous" ... something like that? Showing vulnerability makes us feel exposed, but it opens up way more possibilities for intimacy, in my experience.
You are very welcome here, and I hope you feel a little bit less alone.