Lesbian?

For the last few years I have felt really awkward with my girlfriends, and in my relationship. Sex with my partner I feel like I need to force enjoyment. Sometimes I even feel repulsed. I'm always wondering and wanting to be with a woman. I think back to my previous sexual relationships and distinctively remember having the same uncomfortable feelings. We have a son and I am 24, I wonder if maybe I am a lesbian? I don't know how I could explore that possibility or if I should just carry on, but it seems unfair to my SO, he is amazing and deserves to be appreciated. Should I just talk to him about how I am feeling, or maybe see a therapist first and work on the feelings on my own before deciding anything? Any advice is great, thanks!