My boyfriend is going to his ex's for dinner? please help me.?

My boyfriend of seven months tomorrow's mother is making him go to his ex girlfriend's house for dinner,about 2 months ago he told me that he still likes her and that he is attracted to her and her body and 2 months into our relationship i told him i felt like he needs to pay more attention to me because he told me he can't get over his girlfriend's,i told him i didn't want a boyfriend who can't get over someone while me and him together because i feel like he was more focused on them,anyway he deleted them all on facebook including the one that i don't like more than any of them,she still stares at us and he stared at her all the time,i told him that if he kept it up i would leave him because i feel mistreated and like the second thought besides her. He had contacted her behind my back on facebook because she asked him why he deleted her and he didn't tell me about it then i found out and he tryed to lie to me ( the lieng got me more) he broke my trust with him and now all of a sudden his mom who is very close to me is forcing him to go to her house for dinner?I don't understand why she would do something like this to me when she knows that i love her son and that i don't like the girl ( i have told her before) even though his ex's family and his are still family friend's it still makes me unconfortable knowing that he still had liked her. I told him to stop being a puss and stick up to his mom for once she can't make him do anything he doesn't want to do. If he gives in im thinking about leaving him. And honestly i feel like he will cheat on me sometime with her. I also feel he can't get over her no matter how much he say's he is over her. Girl's how you you feel and what would you do. I feel like im about to cry my eyes out. I don't know what to do or who to turn to.