Is he bi?

So my boyfriend recently expressed to me that he gets bad anxiety because he sometimes has thoughts in his head that maybe he likes guys as well as girls. He's been seeing a therapist (we are both fine with homosexuality, he just doesn't know what's going on, since he has never actually had a crush on a guy) and the therapist says she thinks he's just very insecure which is causing these thoughts to arise. He told me that normally he doesn't get those thoughts but sometimes when we are doing things he gets them. I always can turn him on, but when he gets those thoughts he goes soft, and gets bad anxiety. Does anyone know what this means? I support him no matter what.