iOS relationship advice

I’m 17 I’m pregnant with my first baby I’m 36 weeks so yes sex is uncomfortable and I don’t have sex as much as my partner would like BUT today I woke up in the middle of the night and my partner/ boyfriend was looking at nudes from random girls this is not the first time a few weeks ago I caught him sexting on snapchat should I let him do it or should I be upset or mad I’m not going to lie I was mad just hey he has cheated before I was pregnant so idk it leave him or what I should do pls leave me some advice because I really don’t know what to do