Can someone please help me ?

Right im a 15 year old girl, and there is this boy who lives directly opposite me and hes 14, about a year or so ago we were out talking and we started to kiss passionately and things got very heated, NOTHING else happened, i then started to think ah i wish i never done that i regret it, and about 3 month ago he started to meet my best friend, obviously she asked if it was okay with me, and i said i wasn't bothered as i didn't have any feelings for him, so they were together and one night they were sat outside his house (directly opposite me) and he was saying to my best friend, i love living here its mint, so my friend was like oh why he said, 'because i can see sam getting ready' (sam is me) so my best friend said that's kinda creepy:/ and he said oh it doesn't matter its mint i seen her getting out of the shower one time her body is mint. my friend was pretty sickened by this and he kept saying 'i wish sam fancied me cos id well shag her all over' this is all why he is meeting my best friend, ive just found out this the other day (MY BATHROOM WINDOWS ARE FROSTED) and i just cant help but feel sick to the stomach every time i see his name or his face, ive deleted his number and blocked him off facebook so i have to way of seeing his face, since i found this out the other day every time i look outside i see him, i dint know what i should do, weather i should tell my mam and dad or just leave it, im afraid they wont believe me:/ help me someone ???????????????