I am in love in my sister and i am freaking out. I am 19 year old and my sister is 27. I think it all first started few years ago (4 i think). My sister is very attractive and my stupid friends always teased me about her but i just thought of as a sister, nothing more. Then few years ago she was at some party and she was kissing with girl there and someone filmed them. She is not lesbian but she she got drunk and she did it and video was circling around and my idiot friends sent me video and were teasing me. At first i was angry but soon i got very weirdly aroused by it to the point i started masturbating while watching that video. I can't explain it correctly but at start i still didn't think of my sister in sexual way i just found that video extremely arousing in some pervert way. I felt disgusting afterwards but i was telling my self i am just jerking off on that other girl who was hot. And generally i was much into lesbian porn. However, afterwards that was only thing i would masturbate to, nothing else worked that much. I was watching that video or picturing my sister in lesbian sex. I was telling my self i am not picturing my self fucking her so its fine but i still felt disgusting afterwards. I tried to watch normal porn but nothing worked for me as much, not even close, i always pictured my sister in lesbian sex while i masturbated. Not at first but few weeks later i started to be extremely attracted to her. I know its sick but i couldn't help my self. We still had normal brother-sister relationship and somehow i managed to hide it in front of her and act normal and she had no idea. Several months afterwards she moved out to her boyfriend place which is in different town and later i found girlfriend and my obsession slowly died out. I deleted that 2 min video i had of her even though at this point i knew every second of it in my head, i watched it like million times. I fell in love in my girlfriend and that was it. I saw my sister rarely and didn't think about her in that way anymore even when i did for a while. However last summer she and her boyfriend and me and my girlfriend went together to beach all day. Seeing my sister in bikini all day awaken in me something like never before. I was never aroused like that before to the point i had to struggle all day at beach not to get boner. That night i had sex with my girlfriend and was picturing my sister and had one of best orgasms of my life. Few next months i always pictured her while having sex and also masturbated a lot thinking about her. Soon after me and my GF broke up, we just didn't love each other anymore and she moved to distant town. 2 months ago my sister broke up with her idiot boyfriend and came back home to our house with me and our mom. From then i am totally obsessed. I am constantly masturbating thinking about her. I was seriously considering placing hidden camera in bathroom to film her showering. However i am able to control my self not to. In last few weeks i was stealing her panties from dirty laundry basket to masturbate with, only to secretly return it later ashamed. I think she started to sense recently that something is wrong with me but if she knew the truth she would think i am disgusting and sick. This has turned into more then sexual attraction. I am totally in love with her and obsessed by her. I am freaking out and don't know what to do.