Fiancé cheating?

Soo.. last night I re-downloaded my fiancé’s tinder app on his phone.. I’ve had a gut feeling for a couple months that something was wrong. I went into the message tab and there was messages between 4-5 different girls. All of them pretty much saying the same thing, “I don’t know if you’ve been told this before or not, but you have a beautiful smile.” Literally the SAME THING, he said to me on tinder when we first matched... whenever I confronted him about it he said it wasn’t him messaging them, that it was probably his ex messing with his stuff because she has his passwords to his accounts, then when I handed him his phone to look at them, he DELETED ALL the conversations.. Also, I found a receipt on his phone.. saying he bought Tinder Gold in June of this year.. (we’ve been together since last year). One of the messages had the same date as the purchase of tinder gold. I was up all night crying, and begging for him to just tell me the truth. He still will not admit to doing it and still wants to stick with his original answer. I was pregnant with our baby girl around the time this happened as well. Am I crazy? Should I believe him? To me there’s no possible way she could’ve bought tinder gold off of HIS phone/apple account. But he’s still sticking with his ex doing it, not him. Idk what to do. I’m hurt, my heart is shattered.. what should I do?..😞