I Am a Sensitive Person

I was never a sensitive person until my most recent relationship. I use to have such tough skin. If someone said something it just rolled off me or I'd say something equally or more insulting. I ruined my relationship recently because I kept breaking up with him. If I felt he didn't want to see me because he said the smallest thing I assumed he didn't love me and it was a matter of time before he ended it. So in order to avoid that I would break up with him and tell my self I was letting him go because he doesn't love me. And if cry until she got back together. He did love me but I didn't see it. I was so insecure. I couldn't help myself. I broke up with him so many time it drove him away. The old me would think this new me is pathetic and weak and who would ever cry over any man or person. The old me thought everyone is temporary and replaceable and one should rejoice at the chance of being single and meeting the next one. Not this me depressed and struggling to get out of bed. What happened to me?