Why am I so obsessed with his ex?

[Silentlycringing]

I met my husband in high school. His ex and him started dating back then. I moved and cam back 3 years later and we happened to find one another on myspace. I just left my highschool b/f and he and his ex finally broke up. He was heart broken and we were just going to be friends with benefits and fell in love. Well when she found out it was me his high school crush he was dating she wouldn't stop texting and calling him. I asked her not to call and she called me a bitch and told me not to answer his phone. I didn't have a phone and we lived together and we shared the phone. Well this continued even after we got married. She then got on myspace and I won't lie I looked her up to find that she already found my page and was going on about how fat and ugly I was. She was very fat in highschool and got thin from doing speed. When I am happy I gain weight. So yes I am a tad chubby but not obese. Well when she found out we got married the blogs and text messages continued. I will admit I was a bit amused with the drama because in my eyes I won and I enjoyed rubbing it in. I rarely said anything directly back to her. 6 months later we found out we were pregnant. In between all this the messaging and blog wars kinda cooled down and kept flaring back up. I am just as guilty! But she was always the one to initiate it. I decided I would be MORE annoying than her and see if that would work. It did. Well I was about to have our baby and she started her crap again. So I finally wrote her and was like look we are both adults and I am willing to say sorry. I told her that because of the great changes in my life I don't have time for this drama.... well that worked. Kinda... well now I am just as obsessed over being better than her. Being everything she isn't... I know my weight has a lot to do with it. I am insecure and I had my daughter 4 months ago and still am not as small as I was. I google the ex and read her old journal. It has been a kind of obsession in knowing her. I don't really understand it and I want to stop but I just can't seem to not let my mind wander there through out the day. Believe me I am a busy mom but I still manage to find time to do this odd obsession. Can anyone help me understand it? Perhaps, that is the first step in letting it go?