Advice needed

So I've been sexually involved with this guy he 24 I'm 17 were not in a relationship but he's the only guy I mess with. I'm still in highschool and still have guy friends and he gets mad when they are on my snapchat. Well recently he had this girl in his snapchat but from what it looked like they were on a date and he keep snapping her butt I got really sad and started crying and texted him and said glad your having fun. But my question is should I be as mad as I am