Advice?

Long story short, my boyfriend and I have been together for 3 years now. We have a 18 month old together and I’m currently 18 weeks pregnant with our second. The past month he’s been going up to jasper for work and home on the weekends. 2 weeks ago when he came home, I found nudes in his photos. At first he said he was on Instagram but later told me he got them from the internet. He fought with me about it. Yelled lots; even in front of our son. (There’s been history of cheating in the past) but what gets me now is its difficult for me to get him hard, he use to never last longer than 5 minutes in sex now can last up to 30 minutes, he barely touches me. I don’t want to accuse him of cheating cause it’ll be a massive fight but I have a feeling he is when he’s out there. I don’t know how to go about it cause of how it turned out last time. Any advice??