I'm 13 and having trouble with a couple at school...?

I'm 13 years old and there is this girl called samantha and she is going out (boyfriend and girlfriend) with my ex. I'm not bothered about this but i saw the boy (Billy) hugging another girl and just asked samantha if they fell out because Billy cheated on her, she said no and i just said oh ok then i heard in the school corridor. And know where ever i go Billy is really horrible to me and he is turning all my friends away from me even though i didn't mean to do anything wrong, but he thinks i was trying to split them up. I don't like Samantha and i hate billy anyway, but to be honest she can do a lot better than him, my friends have started to leave me out a lot and this makes me feel quite upset and lonely, and billy and samantha have started spreading stuff about me that isn't true. I'm sick and tired of it. Someone give me some advice when i get home from school i just go in my room and cry. HELP e what can i do to make it better!!