I'm having a melt down every time I'm alone

katie
okay so me and my SO had been sleeping together for 4 months before we got together properly he's a good looking guy and I was aware he was sleeping with other people too, in the fourth month another girl I know he had been sleeping with was comin over on holidays and I asked him not to do anything with her, a week before that I got v drunk slept with someone else and said nothing, te girl arrived he was so good went him with me every night. one day he went to the pub at 3pm and I got a call at 1am that night that he was seen leaving with her, I went to his apartment and found them both naked, he claimed they never slept together which I believe cos I know when he's drunk it doesn't always go up but that doesn't matter the intentions were still there, she left and went home to Ireland (bare in she has a 3 year old daughter and the father WHO SHES STILL WITH, oh they live together and everything) but yeah I admitted what I did wrong too and forgave him but every time I'm drunk what he did fuckinf haunts me, I know he cares for me now, cos I saw his pain when I told him what I did, it was a week after I found them together in bed when I told him, but I still get fucking haunted by this bitch, how the fuxk do I let this go someone please advise me, she's gone out of the country and me and him are happily living together but I'm still paranoid about when she's here next please help me, I feel like I'm going to ruin this relationship before we Even start is properly, this event happened in August and it's still annoying me heeeeeeewllp