I have trust/jealousy problems, how do i overcome my issues?

I have been with my bf for 3 yrs. i love him alot and so does he. he has never given me reason to doubt him at all. but wenever hes playing a new videogame and there are semi naked women in them i get really jealous and angry. i start thinking that he might like them (im a petite person and most of these women are very curvy) and so i kno its because im not dat confident with my body. but now my bf has started a new school and there are girls in his cl (before he went to an all boys school) and i cant stop imagining him thinking about this particular girl. i kno he wont cheat but i cant ever accept he might find another girl attractive. i get angry and scream and cry and cant concentrate on my exams. he says he doest like her but i just cant believe him cuz shes pretty. i dont kno how to deal with dis at all.. i really need help