Why are the feelings soo strong?

How do you get over someone? Even though i know i deserve better why can i seem to get over him? Cause even after i get treated like shit why do i keep on loving this person soo much? He’s never done anything for me yet i want him. I know im stupid and I’ve thought about it soo many times “why am I still there?” I can’t leave and i don’t understand why.. im tired of it.😣