I have a crush on my best friend

I have a crush on my best friend, He has known me since I was in 5th grade but he's one grade ahead. He has known I liked him since last summer and he has a charm I can't resist and let go even though he's done me wrong before I can't stay mad at him but the thing is he talks to so many girls and they all text him and all but he sexual texts them. Btw he said he would be willing to go out with me but he needs time (him and his girlfriend just broke up in November) but he talks sexually to hid friends and once he asked me to be his friends with benefits but my sister told me to leave him alone and I can't seem to whenever we're at school I talk to him but when someone else comes up he starts talking to them and acts like we were never even talking and I'd just stay there waiting for him to finish his conversation I asked him to be my valentine last night but he said he doesn't know how to answer that question and I need help idk what I should do I have mad love for this guy and can't seem to let him go but it's hard please help me please please please