What is wrong with my man (warning long post)

Little background: we've been together soon going on 7 yrs, we've had minor problems in the past nothing major. We went on a break for a bit due to I had a family emergency and had to go take care of a family member 20 hrs away for a yr.

So there's this girl my hubs dated when we took a break a few yrs ago and he stopped talking to her and we were doing SO GOOD until we got married. Anyways I went snooping through his messages bc I just had this feeling so I go and see him talking to her AGAIN 2 months before we got married (I found this after) . Well this girl and him were being so flirty to eachother " I need this positivity in my life" when she'd send him pics. (I'll post them after I figure out how to blur her name) . I found them 3-4 months ago well anyways this asshole tells me he added her on FB again bc he seen her in his suggestives and hasn't seen the baby lately (NOT HIS KID) like why would you care to see how her baby is doing like you never even met her kid before ya know and then says he went to bed and woke up and she messaged him saying "I can't deal with you married ass" like I don't get what is so hard to understand I don't like this girl for obvi reasons and he still finds "reasons" to talk to her. Ive told him before if he wants her he can go have her but I don't wanna be apart of it he of course says no I just want you and he don't want someone that got herpes. anyways thanks for listening to my rant. Any suggestions on what to do next is greatly appreciated.i don't want a divorce I do love him greatly,I just want to know other steps to take before my last resort(divorce him)