Hey, I'm 18 and I just need to tell this to someone.My boyfriend (19)....ex boyfriend... I don't really know anymore. I need someone to help me figure this out.Ok so him and I have been dating for over a year now, we were perfect together. Everybody thought it'll end up by marriage. Except it won't. Last week, I was out shopping with my friends, my parents weren't home for that whole day and my older sister (17) was home. We used to be extremely close. She was my best friend. I told her that I was going to stay the night and my best friend's house. Truth is, I wasn't. I was going to surprise her and buy all the stuff she likes so we can have like a sisters night.Anyways, when I reached the house, I heard voices coming from inside. I entered anyway thinking she had friends over but when I went to her room and opened the door I....God this is so disgusting to even write, I saw her and bf having sex.A wave of emotions washed over me. Sadness, betrayal, anger, disappoint, shock. I just stood there untill my bf saw me. He got up quickly and took all his clothes and just left. Without a single word.I talked to my sister, she deeply regrets it and she feels guilty and she told me it was just in the heat of the moment but my boyfriend.........I haven't heard from him since.Now I just want to know what I did wrong? I was never clingy or anything. Whenever he wanted to have sex, I didn't refuse. I can't tell anyone because I don't want my sister to look bad in people's eyes. For my boyfriend, I know I should hate him but we ahd over a year together, I can't forget our happy memories. I stll miss him, love him and I don't know what I've do if he just hugged me and looked me in the eyes and told me that everything is going to be okay. I'm very weak, I know I'll forgive him.I talked to a stranger about this, he said that if my sister is hotter then I can't blame the guy and we'll, he's right.Anyway, if you reached the end, can you please give me advice? I feel lost.