need help on what to do, please read my story and help me before i make the wrong disision

I love my partner very much we have been together for nearly 7 years and lived in London for nearly 3 years, before we moved hear i trusted him 100% i was so happy, A year and a half into moving to London things as i thought was just as normal but then he told me about him chatting to a guy on the net, i was angry but i trusted his word, then i was at work one evening and i tried to call but no answer then i got a txt saying that he has gone out with this guy, then i just knew something was going on, when he got home home in the early hours i asked him all the questions anyone would ask but he said no he wouldn't do that, a week after i was working again i txt to c how he was the he replied he was at the guys house, i just knew from then the was having an affair, when he came home i begged to tell me the truth then he did, the week before he did oral with him in a bar toilet and then he told me he had sex with him, i was heart broken, we talked and i asked why. the next day i asked him where he was going and he said he is going to the guys house, i was so upset and confused because it wasn't like him just to leave me while i'm in such a state and an emotional reck, i carried on and went to work and then i got a txt saying that he wasn't coming home, i just collapsed on the floor, and my boss told me to go back up north where family are so i did, a week went on and still no txt or call from him, i went back to London on the tuesday then he txt saying that he is coming home because this guy is moving out of london, when he came home we spoke and ever since we have stayed together, im now having these thought to leave because i don't trust him but i love him to much, im so confused and dont know what to do, i have tried to talk to him about the trust issue but know matter how much i talk nothing happens i still feel the same way, i'm scared that he will do it again and in the back of my mind i think he will because he know that i will take him back like last time, please can anyone help me before i fell that i have made the wrong disission