Break Up/Grief

We broke up end of August. After 6 years. The kids told me he has a new girlfriend and they’ve met her.

Just wrapping my head around it all. It hurts. I still see them a bit. I love them so much. We haven’t even been broken up for 4 months and he is already so serious with someone that the kids are meeting her? Ouch. It makes me feel tremendously replaceable and easy to get over.