I am sorry that you are having a difficult time. OCD is cruel and it is relentless and it the doubting disorder, so it plays havoc on us. The trick is to use ERP tools to navigate that, because the more you resist something, the stronger it becomes. And I am guessing here, but you said I don't want to be gay - and that is probably playing repeatedly in your head, so instead of calming you - it is having the opposite effect, because your reaction is telling your brain there is something to figure out. That is why OCD is so difficult - and all of us with OCD do this - we want the anxiety to go away, but ERP teaches us that we can have a good life even WITH the intrusive thoughts. Not knowing where you are on your journey, I will offer you a few suggestions of things that may help you.
First, you can use the non-engagement technique of recognizing the thought, but not engaging it, not judging it, but acknowledging its presence. Say something like, that's interesting, or maybe I am gay, but I may not be, I am not sure and I don't need to figure it out now. Or if you are in a relationship, you could say maybe I am gay, but for now I am going to continue my relationship with my partner and if I fall in love with a person of the same gender, I will deal with it then.
Second, you could really push the OCD to the limit, but don't do this if you are not comfortable. When the thought comes in, say, hell yes, I am gay and I am going to sleep with this person, and that person, and if that isn't enough I am going to find more people to sleep with and I am going to enjoy being gay. It gives the OCD nowhere to go, and practicing that will help bring the anxiety surrounding this down over time. This is a high level exposure, so do not do it if you are uncomfortable in any way.
I hope this helps you.