Is This Childish??

So my fiance ewas with a girl for almost 10 years before he met me. They hadn't spoke in about a year when we met. We've now been together going on 3 years. I used to get so mad just hearing her name (I was 19 when we met, he was 25) I've worked in a few public places where I've seen her and we've ran into her together before so she knows who I am. I would see her and start feeling butterflies in my tummy and get jittery couldn't stand still. Now that I'm pregnant, I don't. She got married and had a baby in November and we were looking at baby stuff and she came up behind us. I smiled at her and we continued to look. No butterflies. I was cool as a cucumber. He, on the other hand, they had a really nasty terrible break up so he got a little aggitated seeing her on the same day in the same place we were. He hardly goes shopping with me so it was pretty odd she'd be there at that exact moment.

I've also seen the girl he lived with before me and got mad when Id see her bc of some drama stuff that happened in the beginning. Im cool as a cucumber seeing her now too.

Is it childish that him getting me pregnant is what's calmed my jealousy??