I'm so confused with my marriage

So I have been feeling like something is going on with my husband for a few months now, I just couldn't put my finger on it. I'm pregnant so for the most part I blamed it on my hormones. All my friends would tell me to check his phone that when you feel like something is going on there usually is... well i couldn't sleep the other night my anxiety got the best of me so I grabbed his phone. Of course there were no text messages I'm sure they would be deleted anyways. So I looked at his emails where I found he had been talking to other people... by people I mean men and woman and even couples about hooking up... he was telling them he was bi. I kinda feel like this is something he should have told me. I'm so confused and I confronted him and he brings up that I hooked up with a girl in highschool.. I don't feel that's the same I was a 14 year old girl experimenting he's a 33 year old man with 6 children. I feel betrayed and don't even look at him the same. Problem is, we have been married 5 years and together for 7. I can't just leave him I love him. I just don't know how to work through this or if this is going to be the case of him coming out later on after investing more time in this marriage. I just need advice. I'm sure I will get criticized as this is a public form but I need some emotional support right now and don't want to tell anyone close to me.