I can't talk to boyz! inferiority complex! what do I do?

So I always find myself sitting next to a boy and I really want to talk to him, but there's always that mind block saying, oh he's just going to think your weird and stupid- that's not the right thing- ohh what am I going to say? Think! think! I believe I have these mind blocks because I've been rejected and have been made the black sheep of my age group due to an unfortunate activity I did at recess 1st-5th grade that had something to do with running on all fours and acting like a dog.( yeah totally embarring) I know that it's ok not to have a boyfriend at age 15, but I at least want to have a guy friend :( since I don't yet. What is really causing me the most trouble is actually starting the conversation. I mean, if I got through that I can carry a conversation no problem. So plz help!