Should I stay with my husband or go?

My husband of 5 years told me in October that he wasnt happy anymore and didnt know if we should stay together and that he met someone else (as a friend) but that he liked her but she didnt know. So for 2 months I tried to make things better. I was pregnant at the time and wanted to get through that first. Then shortly after I felt unhappy and had been thinking to just break things off. I figured by this summer or fall I would be ready to leave. Then two days before my birthday I found that he had accidentally left open an email account with emails to and from this girl. Nothing really incriminating was said. He did say he wanted to meet with her outside of class and that he had bought her a gift for her birthday. She didnt email him that much. Infact I had skype open and she never sent a message to him. I also found a 2nd email account and his skype acccount (all passwords are now changed). Also in his email account, there were emails from a friend at work of naked girls. I used to not care about some porn (like watching it together) but after I gained weight with our 1st daughter and he wasnt making me feel good anymore (not only with the baby but with not making me feel loved or having my back), I didnt really want it around. He knew that and still hid it from me. He said that this friend at work had told him not to let his wife find it. That is what pisses me off the most is that is friend was telling him to hide it from me and lie to me and he went along with it. At the time he met this other girl we were living with his cousin and his horrible gf...they both were rude to me and accused me of stuff and he never did anything about it. I had cried to him to have my back and he didnt. He said he wasnt happy because of all that stress...but I think that is BS. If he had been there for me, I wouldnt have been so mean as he says. If he had made me feel good, he would have been made to feel happy to. Its true what they say, if the wife/mom isnt happy, no one is. If he had been making me happy by doing stuff for me (cleaning, just because gifts) and having my back, I would have been more into giving him what he wants (s*x, love, not nagging so much). Now I dont know if I should stay or go. He went and talked to the guy at work and said he would talk to his cousin too to make up for everything. But how do I know what he told his friend at work, he never let me listen in on his cell or anything. He said another person was there, but do i really have to hunt another person down to get the truth and what if they lie to protect him? Why should this involve everyone? This is all just so much.