Need advice about this

Hi, I need some advice about a situation at work. I (21F) don't know if I have a crush on my coworker (25M). It all started when our coworkers said we were good together and they joked about it almost every day. After a while a new coworker (30F) joined and she started flirting with him a lot. I started getting really jealous of both of them and asked him if he had any kind of feelings for her, to which he said no and that I was crazy. I was happy with his answer, I'm not going to lie. However, I don't know if it's really a crush or if it's because they're talking that we're good together. He's very nice to me and I feel good when I'm with him. We even joke around with each other, for example, he asks if I missed him and I say no, those kinds of jokes. I know that dating at work isn't very good and I'm a little scared. He told me that he had a relationship at work before and that since it didn't go well, he didn't want it to happen again. And I agree with him. Is it just a crush that will pass or is it something more serious? How can I stop this feeling?

Thank you for reading this. English is not my native languague so Im sorry for any mistakes.