I (F30) upset and annoyed my partner (M29) messaged a friendly text to an ex

For bit of back story been with my partner for 8 years, and throught the 8 years he (m29) has message other people behind my back in more then just a friendly way, has sext other women and when we split up for 6 months i moved back home but he continued to lie to me, sleep with someone else then sleep with me the next night why i (f30) was 8 months pregnant with our daughter. He has promised to change, and in moments he has however I saw a message on his phone to a ex and I asked him about it and to show me the message, he put up a fight about showing me the message and said that he doesn’t have to and out of principle he isn’t going to. And all I was saying if it was just a friendly message wouldn’t have an issue with showing me seeing as he has broken my trust multiple time. He started calling me crazy psycho, however i was express how I was feeling and if im coming across like a psycho its because of his previous actions! and i was also expressing how it made me feel and that if he showed me the message i could then put trust into him. Fast forward today I asked again for him to show me the message (however i go very angry today and yelled at him and said hurtful stuff which i shouldnt of done just feels like he wasnt understanding why i felt the way i did)… however the message is no longer there and he apparently doesn’t no what happened to it but like I explained he would of had to deleted it from the chat, as the women’s name and bit of the message is visible when you open fb messenger app but if you click on her name the message isn’t there anymore. So I explain that it doesn’t look good felt like he deleted the message and maybe there was more to it? He put up a fight and told me to message his ex and asked her about the message and that i would be proven wrong. I didnt do this but He then message the women and asked her basically my partner saw the message on my phone it been deleted what did it say… she then agreed with what he first told me yesterday and now I’m this horrible person and just had him berate me about how much of a crazy person I am and how I caused this issue between us and how he was telling the truth…
Any advice would be appreciated!