what should I do?!? Do I have trust issues??

I honestly don't know what to do / think at the moment. I spent a horrible 3 1/2 years with my ex. After being cheated on (3x) years, mentally abused, cussed out daily, etc I have been very insecure about myself. He would always compliment how gorgeous other women were but never called me beautiful, and always checking girls out, I became very self conscious and didn't like porn AT ALL. To be honest I would always confront him just to be cussed out then told I didn't trust him so I just let it put me down and wouldn't continue the talk. After being saved by my supportive, loving, respectful, handsome ass man I finally started feeling better about myself and lost 75lbs total. My boyfriends step brother (a very good friend of mine) and his wife are very open. They won't mind watching porn, saying how hot or how big of an ass she has comments, going to strip clubs, etc but they have never cheated and are very happily married. Which is amazing don't get me wrong but after saying certain things in front of me and my man make me very aggravated to the point I asked him stop and he did. When I first started talking to my SO I told him how much porn upset me and that it was a deal breaker for me he told me fine he would stop it to be with me. After falling madly in love with this man, getting our own place and already planning to buy a house and start a family in May of 2018, talking about marriage and ready to be with the man til I die, I found something that has broke me once more. Tonight my phone was dead after getting home from work so I got on my SO's phone to check my email the first screen was a women's Instagram and it was all naked pictures of her and said check me out on Snapchat and gave her username I checked his snapchat just to see her on there and another women who had the same. He has been asleep since I got home and I'm so broken I don't know what to do. I never thought this would be happening to me again. I plan on talking to him tomorrow before I go to work but I don't know what to say. I planned on marrying this man and buying a house and starting a family all within a year from now. Ladies please I need your advice I don't have anyone I can talk to about it because it's either his family or my brother which my man and my brother are close. What should I say to him. Thank you ladies so much I know this is long but I just don't know what to do. Thank you for all your advice