MY BOYFRIEND HAD HIS ARM AROUND ANOTHER WOMAN.

I have no idea if I'm just over-reacting, my best friend texted me and said "have you seen so-and-so's (a girl I know) snapchat" I had no idea bc I was sleeping. My boyfriend did tell me earlier tonight that he was going to a party and he was gonna get pretty drunk. So I saw her snap and it was a little group photo and he had his arm so tightly around her shoulder that her breasts were touching him. I'm normally not like this, but this is somewhat affecting me. My best friend also told me that when she was at one of his footy games (bc her boyfriend plays in his team) a workout chick walked passed and he said "you can look but not touch" and she said "i don't think ---- would think that" and he said to her not to tell me. Like wtf, it's not like o would really care if he was checking out another chick, like he's only human. But yesterday I spent the whole day with him (a date) and he would not stop checking out other girls. (Which honestly kind of made me sad) but i didn't say anything. Like it's different if he was checking out 1 or 2 chicks,  but he was non stop looking. This chick he had his arm around, I have no idea who she is.. But his brothers took him to this party.