He's filing for divorce today...

Well my husband told me he is filing for divorce today... It's been almost 3 months since we split up and he's already dating some new girl. It's hard to think that just 3 months ago we were trying to start a family and then bam, he told me he wasn't happy... We have talked about the divorce but now that he's filing today it's got me down. I was hoping we would work things out and then he started dating this new girl. Almost a month they have been together. I don't understand how he moved on so fast. It's clear he wasn't happy for a long time and kept it from me. The only reason why we were trying for a family was because he brought it up saying he was ready 8 months ago. I wasn't but I have it a long thought and decided we would try. It's crazy to think how we went from that to this and him move on already so fast.