Is current boyfriend too involved with ex wife?

So here’s the thing. The first red flag was when we saw her boyfriend in the parking lot and he mentioned that he may be cheating on her. I thought it was odd that he new that information but blew it off. The next thing was when we had a pregnancy scare and he texted her, “ I need to get snipped”. That was a low blow to me not knowing what I was going to do. The next thing was he texted her on her birthday, happy birthday baby mama”. I confronted him and he said it was a joke and she hates that. The next thing was when he claimed I used more data then him so I went online and his text log popped up and I realized him and her text all day long. Actually I confronted him on this because they text more than we do. He screen shotted 3 pics and showed me saying it was all about his son. Tonight he had to keep his son longer because she had a dr appt. he then told me she was at the same plastic surgeon I saw. I asked him if she was getting her boobs done. He said idk she HAD mentioned something about it, sounding as if they had talked about this prior. I said how do you even know she’s at the same doctor? He said because I asked her if everything was ok when she said she had a doctor appt at 4:30 because he cares. I told him that’s really odd. My kids dads and I keep it simple, as in, hey I got a dr appt. ok cool see you when you get finished. His life is not my business especially considering I’m in another relationship. He then told me to get over it this is child’s mother. I just feel as if they have unfinished business considering they just got divorced 3 months ago when I pushed the issue, although he said it didn’t matter either way considering they had been separated for 5 years anyway . Mind you I am 3 months pregnant with his child and we have plans to be married next month. I’m not entirely sure if that’s something she should know but considering they know everything about each other why doesn’t he tell her that? I told him it’s just weird to me considering anytime he texts her and only her he covers his phone so I can’t see. He said because I get weird about it and he’s gonna continue to do that. Am I being pregnant and irrational? I just feel way low on the totem pole. I also know that my ex husband and I held on to divorce papers partially because I wanted him back or the thought of sounded good even though in reality it would never work. I’m a pretty rational person and I understand human nature. I have tons to process I’m just not sure I can handle this constant communication with his ex wife