What do y’all think

So me and my fiancé were fighting pretty bad he left for about a week right ok.... so we have been together almost 2 years now. Well his ex gf passed away but they were always on and off together and she was always messing with other people... yes I know her personally... well when they were together before I met him him and his ex had a threesome with my mom says she only sucked his dick... ok well he came back home after a week right... I looked through his phone yes I know I shouldn’t have but I have trust issues ok. Well he has been searching my mom on his messenger her name is the first one on recents. I mean have they been talking what’s going on they both hide things very easily also my mom is a junkie if I asked he would just get mad and say no are you fucking someone what should I do pleaseee any advice would help!