I Dislike 1st hour,! im insecure around this guy i like,!?

well i like this guy, and i think he used to like me but now he's dating this girl im pissed but i try not to show it, and were in the same 1st hour i sit right diagional from him, im shy around and kind of insecure, im scared moving, im scared when he passes me and it turns me on when he passes me and ugh! hes cute but i want to like going to first hour not being scared or shy, in all my ither classes im fine but kind of in math were in a girls & boys class, but idk when i was in 1st grade-4thgrade i was in a boys and girls class and 5th & 6th grade and now 7th grade i feel self consious around guyd and start to shake alil any advice,?