I had sex with my mom's older friend and i regret it completely!

I am 15 years old. I had sex with a 30 year old guy 2 and a half years ago. Before it happened he was super nice he was one of my mom's friends and I remember one day I was in my backyard and he came and we started playing, it was kind of like I was trying to see how hard I could hit him, because he's really strong and muscular. And I remember him lifting me up in the air and when he put me down he turned my back to him so that I could press against his man part and my mom came and she called me inside and she said something like you shouldn't play around like that with guys because they could get the wrong impression and I just remember saying to myself that she was just exaggerating like he wouldn't think of me like that. It happened during the summer time, my mom went to my aunts birthday party but I didn't want to go, so I stayed home. About an hour after she left he came at my window and told me to come outside and so I did but then he took my hand and put it down his pants and then he convinced me that I wanted to do it. I told him to come inside but he wouldn't he said that he wanted to do it outside ( I still don't get why?) and at the time I had on trousers so he sent me inside to put on a short skirt so I did, at the time I saw it as thrilling so I hurried inside and put it on and he carried me to a dark shadowy corner and we had sex ( In all honestly it hurt really bad at first but after I few minutes I actually liked it). After that I went inside and I got cleaned up but when I got to bed and I started to think about what I just did I cried for hours, days and weeks (I don't get why I regretted it tho) I kept blaming myself, I still blame myself I mean I should have known better but I did it anyways and I hate myself for it! I did try to tell my mom about a couple weeks after it had happened but in the sort of middle of it she got a call and she left so she still doesn't know it's eating me up inside I just needed to tell someone. Even today he still comes by my house and he gives me sort of looks and he tried asking me to do it again a couple of times but I keep avoiding him and running away from him and he kept coming to my window asking me to come outside because he just wanted to 'talk' so moved my dresser and put it in front my window. I think its weird though because I used to be afraid of him after we did it I don't understand why though because I said yes at the time its not like he forced himself on me. I think I have gotten over it though but sometimes when I remember I start to cry and that just really sucks so that's it I guess.