How do you get over someone you have to work with

Me and ex (both 18) broke up 4 months ago after being together for 8 months. We started working together since 2 weeks before we broke up and it’s making it impossible to fully get over him. I only work part time so I only see him once a week and every time I think I’m over him I have a conversation with him and it kills me that I’m talking to someone I was so in love and so intimate with so casually as if nothing ever happened between us. I’ve tried blocking him that didn’t work, now that I have him added back we might have the odd conversation about work related stuff and that’s it.It just seems impossible to get over him when I can’t cut him fully out of my life and I’m not leaving my job over a man when I know I won’t get better pay anywhere else at my age. I would really love if anyone had any advice as it’s starting to become a bit of a joke how much I still care when I can tell by him he’s completely over it