Idk what to do


Ok so I recently went through a break up with this guy. He wasn't really the nicest to me but i didn't mind. Anyway, the next day after he broke up with me he starts to date my best friend. When I saw how nicely and caring he would treat her I would be depressed all the time. I also a few times considered suicide. ( idk if I actually would or not but ). I also on Tuesday wrote him a letter saying that i still love him and that i rlly want to date him again and that i hope he still feels the same way about me. That some night he texts me and says ' you should just let it go that happened mouths ago and we are done'. That broke my heart into a million pieces. But I still love him. What should i do give up and ignore him or keep trying? Plz help!!!