Confused & Don't know what to do

I don't know what to do. I've been with my husband 14yrs, married 11 of those years. I have never had a reason to not trust him until now. Month ago we had a big argument. It was enough he left for couple hours, came home and straight to bed and set his alarm for work the next day earlier then usual so he wouldn't have to talk to me. While he was n the shower I looked at his texts on his watch just to see who he talked to about our argument and what he said about me. Figured he talked to his brother or his best friend. Nope...he text his ex wife. That bothered me first, then she started talking about her relationship and how unhappy she is, he proceeds to say things to her like "I wish I could take care of you" ,"You are the most beautiful women I know & so much fun to be around". That all hurt me and has been bothering me. Since then I have looked at his texts on his phone when he's n the shower (I know I shouldn't, so please no fussing about that) he's talking to her everyday, yes they have kids together, but they r n their 20's living on their own. I've seen texts where she said Love You abd he replied back Love you too.....he's sending her money. I hadn't said anything earlier because it was around the time my oldest was about to graduate. Now my kids r at their dads for the summer and idk if I should say anything. I know I'm wrong for looking at his texts, but after seeing those texts when we were arguing, I'm afraid there's something going on between them. Should I say something or try to let it go, that I'm reading too much into it? Any advice would be appreciated.