Is it normal to obsess over my husbands ex?

I am trying to find the pages I was reading before I signed up. I have been with my husband for 6 years and he has a son with his ex, his son is 7 so I have been my step sons mom, we have custody he only sees his mom once a week for a few hours and every other weekend when she takes him. She has done a lot to my husband and I we were in court for 2 years but it was worth it cause we won. But why dont I feel like we won? I can't stand her I know she has tried to get me fired and break us up but none of her tries worked. SO why do I feel the need to think about her all the time and check her facebook page all the time. SHe is the only problem in my life, I know that is pathetic then, cauase my life isw amazing besides her and she is winning cause she makes me crazy and does not know it. But why, I mean we won, I raise her son and have the life she wanted, she is in her 30s and lives with her sister, she has moved like 10 times in 6 years and has like 10 jobs and is looking to move again and get another job cause the job she has not keeps her from seeing her son on her weekends but during the summer my husband and I work with her so she can see her son cause her son wants to see her and it is about him. I hate doing anything for her or even seeing her, someone please help me I just want to forget about her and be happy with the amazing life I have. I know to move on but how???