Watching adult material

@Lostnlonely81

Maybe you should start as a relationship inventory ... and deal with the underlying issues 

You do not want him to watch these types of videos..... felt he was .. you also feel he will lie or say he did not do it....if confronted .... serious trust issues. 

A person that feels you do not respect them or trust them.......   may also feel no reason to quit doing something  EVEN if he knows about your feelings on subject.   

Now where are his boundaries? 

Does he approve of  you going thru his phone?     Snooping as you call it is an invasion of privacy.   So many seem to they are given a pass as a GF/BF / partner to invade a persons privacy not true.  

It takes 2 so what will you do to restore trust that you won't invade his privacy anymore?   What do you want him to do to restore trust that you do not have in him to not lie or watch things you disapprove of. 

@toughTiger6481  Thank you. You are right. I do have serious trust issues and he knows this. He caused it in the relationship. I do love him and would love to be able to move forward but I'm not sure how. For the 1st 5 years of our relationship he was either online cheating, psychically cheating, flirting, or buying porn. I can't seem to find a way to trust him and now finding he's doing this, I feel like its just a matter of time before hes psychically cheating again. I just don't know how to cope and get my self esteem back. I just want to be happy and move forward. I'm stuck. 

@Lostnlonely81

I understand and I will tell you what took me a LONG time to learn ....

it is NOT you........ it is not a reflection of you either....

when a person decides to cheat or other items it is on them.... We internalize it and try to fix whatever we think is the reason.... but if we do not know their "why" we tie ourselves in knots trying to change something out of our control. 

With that past you are right it may only be a matter of time before this ends badly.  Please evaluate your relationship if he can be honest deep discussion about where to from here... because waiting and hoping things all work or change on their own you will regret that time you could have found a person who values YOU and deserves trust. 

@toughTiger6481 thank you so much!  You have really helped me.