I was felt up, played with, and taken advantage of when i was 10.?

Well, i am a girl who is now 14. and when i was 10 a boy who was 15 felt me up. It all started because my mum knew his mum and was good friends with her and he used to come over and just play on the video games with us, no biggy. But then, because my little brother was only a few months old, she used to take him to bed and lie with him for about 20 mins just to make sure he was okay, and sometimes she would nip next door or something and that's how it started. one day when she took my little brother to bed he said these exact words 'want to play a game' and i didn't know what he was on about but before i knew it, he had his hands on my below private area and started playing with it and puttin his fingers in an out, and i went to go the toilet and he pulled my pants down, and then he left. this continued for weeks and weeks, and one time he started licking all of my privates and playing with them and stuff, he made me see him naked and he said 'don't tell anyone about this or you will not live to see tomorrow' i was terrified but i didn't know what to do. the only reason it stopped is because we moved when i was 11 and everything was back to normal. But the other day, i saw the boy who done it do me and he started following me, and i just thought nothing again, but yesterday he knocked on my door and because my mum still doesn't know she let him in and was like, ' i haven't seen you for ages, lets have a catch up, you've gone big' and all stuff like that, he is now 19, and i'm scared he will do it again, i can't tell now because it was like 4 years ago and it would be pointless. but i don't know what to do, someone help me?