Cheating? ....

Ok so here goes I’m heavily pregnant with both mine and my boyfriends first baby who’s due in a matter of months. I had his Facebook password and checked messages which were like fine until .. I came across my boyfriend messaging a women about her friend in work exchanging sex chat and photos of his .... ( you know what) I was in complete shock he is 21 and this women is in her 30s married with kids I can’t believe it my boyfriend is a very good looking boy I understand he gets a lot of attention but never did I think he would have messaged another woman on “Snapchat” and passing messages through her friend on Facebook messenger. I don’t know what to do I’ve not said anything to him he works away and is currently stuck offshore at the moment due to the current situation We speak every day & night but I don’t know what to do .. do I leave him baring in mind these messages were dated June 2019. I keep crying as I can’t get over him speaking to someone sending dirty messages saying “ he doesn’t have anything to lose” of course I don’t know what was said when he was directly messaging her through Snapchat as I don’t have his password he accused me at the start of the year saying I was cheating while he was away. And said I’m always hiding my phone I haven’t ever. He is very paranoid and always thinks I am which has got me to the point I don’t know what to say anymore everything I say apparently isn’t right. anyway, I’m now thinking he’s done more than text, of course, I can’t prove it he always makes me reassure him which I do but I can’t keep living like this I’ve never cheated never done so much as look at anyone else. I’m due my baby in 2 months I don’t want to mess up our daughter's life but can I really trust him? Would any of you leave your boyfriend of 5 years through this or am I just over reacting he also told this women him & I were separated which we never have been?