I don’t want to be heartless

I used to be an emotional hopeless romantic. I let people walk over me and I vowed to not “let guys fuck me over.” But this is not what I meant. I did not mean that I wanted to turn into the one who fucks them over instead. My ex just broke down in front of me & I felt.. nothing. I tried to make myself cry to tear at the walls I built but afterwards, I still didn’t pity him. I lost sense of who I was. I don’t care about how I make other’s feel but I want to care. I don’t want things to revolve around me & what I get out of it. I don’t want to emotionally damage others because others did to me.. what can I do? Like, I care about other’s feelings AFTER I’ve hurt them. But back then, I would’ve avoided it in the first place. Im such a shitty human