Hi Schilling,
Do you mind if I ask a couple of things to clarify?
When you say the last time was March or April, was that the last time you two lived together or was it the last time he cheated?
How much time do you two spend together? During his infidelities, did the APs know that you two were a couple or was your partner trying to convince them he was single? I ask because I wonder if this is an excuse he tells himself - excuse or not, it would be wrong of him - and if it's something he's ever said to gaslight you. ETA: This is something my now-H used to tell himself, I believe - we lived apart, though we were in a relationship and I was expecting our baby, yet I think that living apart made it easier for him to allow himself to feel and therefore act single (though he still continued with many wayward behaviors even after we moved in). In other words, does your partner acknowledge your relationship sometimes and not others and try to be "subjectively" single?
BTW, this is no excuse to cheat. People will have poor boundaries regardless of whether they live together or apart. A person with extra poor boundaries will make excuses for him or herself to "justify" crossing said boundaries. I'm wondering what his excuses, or lies that he tells himself, are when he cheats.
Are you two living separately due to his cheating? Has he ever showed any remorse for his cheating?
Do you have requirements that he would need to meet in order for you two to reconcile? Please don't be afraid to have them. If you could have the healthiest relationship possible, what would it look like?
It sounds like he has a very poor sense of boundaries or that he continually willingly walks over them. A person who tells you not to trust them, who takes photos with other girls, who cheats repeatedly on his partner... It sounds like he has a lot of work to do in order to be a healthy person for himself and a healthy partner for you. Is he willing to change, or does he think things are fine the way they are now? How do you feel?
I notice that you don't want to leave right now. In addition to some other good resources, there is a thread in the "I Can Relate" section for folks who do not want to be told to run: http://www.survivinginfidelity.com/forums.asp?tid=456588
Please keep posting for support. One more question: what do you need to be healthy right now, for yourself? Never mind him for a moment... What about you? Once you know what you need to be healthy, don't compromise your health. Create protective boundaries around your health.
Welcome to SI. 
[This message edited by silverhopes at 7:10 PM, July 8th (Monday)]