I can't keep it up

I'm gay, but I really don't want to come out in high school. My friend and I were on vacation away from home, which is the only place I can really be myself away from everyone I know.We were holding hands in the park, and people looked at us. Nothing rude, everyone was okay with it. I just had to stop and go home, I couldn't take it anymore. It wasn't the looks, or him, I just, I felt so vulnerable. Every time I'm with a guy and not acting like the stereotypical straight guy I feel so open.I don't know what to do, so I came here.