Being the second wife

I am struggling with insecurities surrounding my husband’s first wife. Even though I know that I’m successful, I make more money than she does, I have a better education. I find myself CONSTANTLY comparing myself to her. I get the urge to stalk her facebook page and then beat myself up over what I find there. She’s younger and thinner than I am. Like 8 or 9 years younger than me. She’s caused A LOT of problems in our marriage by using her daughter as a pawn. I know I am making her the villain but I can’t seem to stop. I constantly feel like I’m second best. That she got all of the “Firsts,” and I’m stuck being second. That I’ll never get any of the “special” moments that she did. How do I stop feeling so insecure about this woman?