Found a video of my boyfriend jerking off he admitted he wanted to send it to someone on Kik.

Found a few videos/pics of a girl masturbating on my boyfriends phone that was copied from Kik along with two videos of him jerking off. Confronted him about it and he cried and said it was because we we're fighting. That the videos of her where old but he had thought about sending the video of himself. We talked about it and I thought we were okay but I secretly downloaded Kik to his phone and when I checked it a few days later he messaged a girl "Daddys Back". I asked him about it and he says he has no idea how he was logged in that he must be "hacked" because he permanently deleted the account and he did not send the message. I don't know what to do we've been together for 3 1/2 years, talked about marriage and we spend most of our time together so I never though he'd do this. Any advice would help I don't want to be played for a fool. Thank you.
-N