Trying to get over him

Hey y'all, I don't know who else to talk to, so here I am. So I have liked my coworker ever since I started working here. He is very flirty by nature, so I developed a crush. About a month or two ago, I found out he started dating our other coworker(who is absolutely gorgeous btw), but she was forced to quit because her parents caught her with said coworker. She is not allowed to date due to her religion. So I decided to get over him, which was easy because we were never working at the same time. But today, our hours overlapped, and he was hanging out with her before hand. I saw them kiss, and I felt hurt all over again. And I had just found out that she was coming back to work at my job, (which doesn't make a lot of sense, considering she was forced to quit) I have a lot of self esteem issues, and how pretty and kind she is makes me feel incredibly insecure. And none of my other coworkers seemed to have any qualms with them dating and working at the same place. I'm not entirely sure if dating is banned from my workplace, but I just can't imagine working with both of them. I'm not sure if I'm looking for advice or support, but I just needed to get this off my chest.