cheating

Ok so me and my boyfriend have been together almost two months now and in the beginning it was great. Then later on we went through a really rough patch which he blamed on me, but it wasn't me in my opinion he just started treating me really mean so I kind of shut off and he blames me for the issues because I shut off. Then we finally talked about it and stuff got better. Pretty much we have been going fine, i mean there has been quite a few bumps but nothing we couldn't work out. I had been suspicious over some things that seemed not right. Two of his friends came to me saying he was cheating and told me some other stuff he had been supposedly doing. Some stuff I believe some I don't like him flirting with out her girls I did believe mostly.  But last night my friends got a hold of his phone (he never lets me look at his phone or freaks out if I get near it. He also never posts anything about me ever.) and they went through a little bit of it until he figured out that they took his phone. They found another girl in his phone that he had been cheating on me with. My best friends took pictures of some of the messages off his phone with their phone. Now I have the proof he is cheating but how do I confront him and call him out on it without him being mad that they took his phone. Knowing him he would turn it around on me trying to say I made them do that or something.