Someone help me

I had been with my boyfriend for nearly 3 years we are both 16 years old , and about 3 months ago i noticed he didnt have much time for me anymore and we spending alot more time with his friends which i obviously thought nothing really of and just left it. He had also been lieing to me alot about where he was and who he was with.However, he had also been spending time with his best friend Nathans older cousins which are about 23/24 years old. Exactly a month ago today my boyfriend dumped me, he had ignored me for 4 days leading up to this and i couldnt take it anymore so i decided to go to his house and ask what was going on; however, when i got there he wasnt there and his parents asked him to come home and when he finally did he was in the worst mood in the world and told me he didnt love me anymore and that it was over. Since the break up so much has happened he has a new group of friends along with nathan and he has started doing weed which is so bad because he has got into a football academy and he will ruin his future he is alsoi being added by lots of other girls which hurts me alot I had found out from one of his best friends that he slept with one of the 23 year olds i did find it hard to believe at the start but then i found out she had also been buying him expensive stuff and taking him to theme parks he also had pictures of her on his phone. I got so so angry that I put it on facebook which now i really regret because he actually hates me and has been calling me such horrible names whilst denying it i really do just love him we have exams coming up and i took some revision notes for him round his house and texted him and he didnt even say thankyou i just want him back, i want the person he used to be back!! i want to show him how much i love him and how much i care but i just feel like im pushing him futher away please help me someone xxxx