Attraction problem............?

i keep getting attracted to problematic guys. i dont know how to explain it but not only i find their messed up minds interesting but i also pity them and i wanna take care of them. its like it makes me feel good that i'm giving love to someone like that and that i might change them for the better. so far i have been with two mentally deranged guys and both times it ended badly. and now im finding myself falling for another screw up. and i dont know how to stop myself from feeling for him. i wonder where does this stem from and how can i talk myself out of this? i dont want to go through pain again yet i find it hard to stop :(