Broke up with him 💔

I broke up with my (soon to be) baby's dad last night. He wanted to get back with his ex if she'd forgive him and for some reason in my gut I knew that. It hurts though ya know? And I work with him in the same department. I know he'll be there to support the baby cause he already has three kids. But, it just....hurts. How do I do this alone? I'm terrified.Â