Should I Let Go?

Well me and my boyfriend have been together for almost a year now, Everything was fine the first couple months into our relationship. I was told by his family I was the first girl he has actually brought home. His mother continuously tells me how much he cares for me and how happy she is that her son has found a good girl. But for the last 4 months it seems like he really doesnt want me any more. We havent been intimate (sexually) for the past 4 months and even though he tries he just cant get the job done. I have gone through his phone and found a girls picture in his photo album on the phone. I had confronted him about the picture and he swore on his mother and little brothers that he has not done anything with that girl she is just a friend. I still havent forgotten about that but I left it alone and continued to be his girlfriend. About a month ago I called him one day because he hasnt called me all day which was kind of wierd on his part. When I called he seemed very different and lost in words. I asked him what was wrong and he told me he just found out he had a 5 yr old daughter he never knew about. When he told me that I simply thought he was trying to break up with me. He told me he wasnt trying to break up with me that he still wants me to be his girl. But ever since the incident with the picture on the phone he has detactched himself from me. I just dont know what to do. I love him very much and I know he is a good person inside. He says he is just confused with everything that is going around. Should I let him go? Please Im seeking for help because Im also confused. Feels like im in a dark tunnel and cant find the light.