[Advice]My boyfriend thinks i'm straight what should I do? I'm afraid of sex because I have a small penis.

To start I am a 22 year old male who is currently a virgin. I’ve never been in a relationship with another guy before. I have had quasi-relationships with girls before but I didn’t want sex. I am now in what I consider my first real relationship in my new life. However, I have a big insecurity with sex because of my penis size. I have been feeling more insecure about it since I started college. I'm only a bit over 3 inches long and according to http://ift.tt/1NIhJUB I should be over 5 inches based on my stats. It makes me feel very scared to engage in any sort of physical relationship because of my insecurity. The last 7 months I've been talking to this guy, my now bf. We met at an EDM event. We've become "official" as a couple but we haven't had sex yet. I felt so happy to have a relationship, being close to someone feels good. He is not a virgin though and has been comfy in his sexuality longer than I. Recently we got into an argument because he thinks I might not actually be gay and that I am just experimenting. He said that he thinks I am bi and that being bi is not a real sexual orientation. This was hurtful to me. I am not bisexual. I know I’m gay and I am fully sexually attracted only to men. I don't know if I should explain my insecurities to him. I don't think we can continue as we are. What should I do?