Cheating Boyfriend?

My boyfriend is obsessed with women, porn and sex. We've talked about this problem and fought 3-4 times. This past time I left him. I didn't know what else to do... We talked more and I told him we would try this last time and that these things needed to stop 1000% percent. I feel like since I promised him this, I need to stick to it and work hard to help. But I'm just so angry with him. And I can't trust him enough to send him to the store to get an ingredient for our dinner! Has anyone else stayed with a cheating boyfriend/spouse? Please don't be mean... My heart is broken to pieces and my world seems like it's falling apart...