Hello everyone

Okay so as of right now me and my fiancé are not talking. My fiancé lives with his mom and I live with my parents but back when we were dating his mom would constantly call while we were spending time together on the weekends. He would stop what he's doing to answer the call (even if we were starting to get intimate) It bothered me of course and he told her to chill and she did. Well she ended up getting a divorce so now she would text him all the time. I brought the issue up again and he told me it was cause she was alone at the house. So now she is getting married again and spends her weekends with the guy yet she STILL texts and calls my fiancé friday-sunday when he spends the night.
So now last weekend he was texting her and she would call him while we were hanging out and I overseen him texting her that we were on our way to the fair. I could definitely be wrong but I could have swore I seen the word sex in the text message which had got me very interested. So that night I went on his phone to read the conversation between him and his mother and he had deleted it! Other convos were there from days before but his moms was gone. I brought it up to him and we got in a big fight was I in the wrong? I mean she texts him in the morning through the day till he goes to sleep I can't help but think they talk about me? :(

Were moving together and I don't want things to progress. Ill have to leave him if it does. I think it's just ridiculous