Farting..????!!!!! help please?

im always farting and it gets really embarring and once it starts i get really like worried and stuff and embarred and then i keep farting and they get louder and smelly and when i have tests i fart sometimes and now im scared cus have tests in up soon im so scared..please tell me wats rong im only 14 im freakin out like...im overweight but im trying to lose weight..i dont think my diet is that bad..but i have been told i eat fast cud that cause it..??and also one time i had to leave school in a middle of a test cus i felt so sick and i kept farting and when i go toilet when i feel sick and have farting i have dihoria its soo embarring please help would be much appreciated and please no nasty comments im self conscious enough about it as it is