My ex

Me and my ex broke up about 5 or 6 months ago. When I tell you I miss him so much its unbelievable and it's kinda crazy bc he cheated on me multiple times, was manipulative, and kinda mentally abusing and for some odd reason I miss him more than anything. I just wanna kiss him again, hug him again, sleep on his chest again, and tell him I love him again. He is far from what's best for me so I don't know why I want to see him so much. This boy was my first love and I still love him. Why does it take so long to get over someone? I shouldn't still be crying myself to sleep because of how much he broke me, I shouldn't still have those chest pains when I think of him, and I should even miss him..... but for some odd reason I do a lot.