I really need advice!!

Sooooo I’m pregnant an I know I’m going to be emotional but my fiancé is making it where I don’t even wanna be with him anymore. Ok so here is the problem we have a open an honest relationship well at least I thought it was anyway he had a heart attack and I was going threw his phone to find some numbers an I stumble across a few messages where he talking about he need a head master he need for this chick to suck his dick when he wants her 2 now when I confronted him about it he said he wasn’t really going to cheat but In the back of my mind I feel like he lying because now he stays deleting messages an always saying shit that he knows going to hurt my feelings like I wanna leave because I have so much going on my grandfather died an it’s like I’m alone but I also know that love isn’t easy an it takes time an forgiveness I’m just confused I’m at the point I wanna just give up