I caused another girl pain and don't feel bad about it. Should I?

My fiancé and I have been dating on and off for many years. I messed up and didn't realize how much in love with him I really was. We were dating when I met her, but she was a threat to me: pretty, sweet girl (so I thought) and loyal and my insecurities kicked in. I was afraid that he would fall for her and leave me. I demanded he cut her off immediately, he didn't and I dumped him for a guy who cheated on me. I tried to go back to him, then he rejected me and I find out he's now with her. Apparently she'd been in love with him all along. I was miserable. We get back in contact and I realize that I'm still in love with him, he tells me that he misses me, misses making love to me and that he couldn't fall in love with her because she's one of those goody two shoes Christian prudish girls who don't have sex before marriage (every guy I've been with raves about my bedroom skills on the other hand). We get back together and of course he doesn't tell her (I made sure to tell her to back the hell off though).

It was as though he was waiting for me to come back and say I was ready to settle down. I only had to say "I want you back" and within two months we were cohabiting, looking at houses, engaged, planning for children and have a wedding date set for next year. All of our friends want us to be married except this bitch. We invited her to the engagement party and she said they weren't friends anymore because he dumped a faithful woman for cheating slut who will never be faithful. From what I heard, my stealing him hurt her so much that now she doesn't want to fall in love with anyone ever again. I told her that I'm not going anywhere this time and to get over it. He feels bad about causing her pain but I caused her pain to and I don't. Is there something wrong with me for that.
I caused another girl pain and don't feel bad about it. Should I?
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