Spring break

HELP!!!
So me and my boyfriend have been dating almost a year. He's 24 and I'm 20. For spring break he is going with 2 of his friends (one of them is bringing his gf) to south padre for spring break and since I'm underage I'm not going. I'm worried that he is going to cheat on me because spring break is like a giant hook up fest down there. He said he would never do that but when u mix alcohol and girls in bikinis into the picture I just get really worried...what do I do:(