Am I wrong

My boyfriend and I are in a really great relationship. I'm happy and he's happy but there has been this one block. About a few weeks into our relationship he got back in contact with this friend he has been friends with since high school who is a female. She's engaged and is a sweet person. Although I don't have a problem with him having friends, they started texting and hanging out alot and there were many times I was at home by myself while they were at her place hanging out all day while her fiance was at work. She'd message me and tell me what they were doing and send me pictures of how fun it was. I felt left out and like a third wheel, which I found odd being he is my boyfriend. He'd spend the night over there , although her fiance was there during the night I didn't feel comfortable. They play dirty question games, etc. There was once I was over with him, her and her fiance. Their place is extremely small with no doors to other areas. She went into another area to change her top and told him and I not to come in. He didn't hear her and ended up looking. He was very upset with himself for that but my concern is how many times has this possibly happened while they were hanging out all day at her place. I felt like none of this was appropriate. So in the meantime I tried to befriend her because after all it was his friend and this friendship means alot to him. I allowed her to spend the night over my place and we did have fun and watched some movies, I felt somewhat comfortable enought that I brought up the situation and how it was making me feel. She told me of course they are just friends. Later she ended up telling me that back in high school of he never dated his ex he would have dated her, that I shouldn't be jealous just because him and her are closer than him and I are, etc. He got upset with her about saying those things and she apologized to me but for me that wasnt enough ans it sisnt ease my heart. There was a night he went over to her place while I was at work without mentioning anything and from her I found out that he told her not to tell me about it. I later spoke to him about all of these occurrences. He said that he didn't have anyone to talk to about me and our problems regarding this and my doubting. He feels none of this stuff was wrong and that he should be friends with her because they've been friends for 7 years. I thought the situation was cleared up after talking multiple times about it. He finally told me he'd just cut off all contact with her, but somehow the other night he asked me how I felt about her and if I still disliked her. That went into an argument about how he feels he isn't wrong and that he's not allowed to have friends. He called her and told her that i didnt want them being friends. I thought this all got solved. To be honest I'm tired of arguing with him about this. I wouldn't make him feel this way. I would understand where he's coming from. Am I wrong, is he wrong, what should I do? I love him and he loves me. He does so much for me etc but this situation has damaged part of our relationship.