Should I stay or should I go?

Me and my boyfriend have been together since day one. As soon as we met it was like a dream come true and I moved right in. Well a month went by and things started to change. We didnt have sex like we use to and we started seeing couples together(swinging). Well our intentions were to find a girl who would be interested in having a three some with us because I wasn't comfortable sleeping with another man. Now it's an everyday thing he's on the site atleast 6 times daily looking at couples and girls for us to meet with I've told him I dont like how often he does it but then he hides it from me when I say that. Another thing is I had found out from his ex that he's cheated before and that he sent her an email saying he missed her ( she screenshot it) I feel like there's no connection between us anymore and I dont know what do? Someone help.