Struggling with Coping

[anxus11]

My Boyfriend and I have been on and off for 5 years. We started dating in high school and we had a very rocky start. He cheated on my a few times in the first 2 years, but we have worked very hard on rebuilding trust. I know that high school relationships are so trivial compared to actual adult relationships and I realize that we both have changed and grown so much. I trust him very much and know that that phase of his life and our relationship is long over, but there is just one big problem that I can't seem to get over. The problem is that the girl he cheated on me with was in our group of high school friends and I constantly have to deal with hanging out with her and him together. The problem with this is not that I'm scared something will happen, but simply that bad memories flood my head. I don't think it's fair for either of us to give up our high school friends but I don't know how to deal with the memories that arise when we are in this situation. I know that with time friends will move away, start families, etc. and we won't have to deal with this, but how do I cope with this until then? Is it possible to deal with this, and if so do you have any advice? We don't want to break up. We love eachother so much and he tries very hard to make these situations easier for me, but I just can't seem to deal with it! Any advice???