My boyfriend had sex with someone else while on a break, I dont know how to feel.?

We are on another break after I found out he had slept with two girls while we were on our 1st break. Our 1st break happened because we were constantly fighting and we had a huge argument, so we decided to leave eachother alone for a while to see if we should really be together. Once all this happened we got back together and now about 4 months later, we're fighting again and he confessed he slept with 2 girls during our break and lied to me about it. I don't know how to feel, Im more upset that he lied to me then about him having sex with those 2 girls. Then he says "because of our problems he slept with those girls, that if we would have been ok it wouldnt have happened" I really dont know what to think or do. HELP!