What's wrong with me

So this is a long story and I don't have anyone I can talk to about it. Anyways it's been three years since my ex and I ended. We were both bad for each other and I did a lot of mean things and so did he. I never cheated on him but he did cheat on me many times. I finally had enough and left I met my spouse really quickly afterwards and got pregnant. We decided to have the baby together now we are engaged and have a second child together.

Anyways his ex recently messaged me and told me he cheated on her with a married women and nothing but heartache filled my head again. It's been three years and he still has that affect. I ended things cut him off completely we had a house together everything but I don't understand why he still crosses my mind. I love my spouse with all my heart and he is amazing to me and an amazing father. But I feel like my ex gets everything and he's a horrible person and I don't understand why he never struggles pretty much why do bad people get good things. I feel like I honestly didn't grieve properly. I dk what's wrong with me but I have been waking up every night and upset and I don't even know him anymore or love him.