My bfs going to Ibiza on a lads hol?

Im 19 and he will turn 21 on holiday , his going with ten lads and he is due to go in 3 weeks , we have been together a year on and off , i love him so much , i never had reason not to trust him b4 but im sooo scared his gonna cheat i cant sleep or eat i feel like i will have a break down when his away , i been hurt badly before , i just cant see how he wont cheat when all these hot girls are around throwing it about and under the influence of alchol , please help me i need advice what do i do? His the guy i know i wanna spend my life with