Mixed business w/ pleasure

I started seeing a co-worker who is 9 years older than me, thought things were going pretty good. We slept together a couple times. Still thought things were going good and then all of the sudden he tells me he's seeing someone and that it's serious. I'm a ball of mixed emotions. Things were good and then this? Out of the blue and his only response is that we work together and this was just bound to happen. We were pretty clear that we would keep work separate from what was happening outside of work. We'd never talked about things just being a hook up but we also never talked about a relationship. I just put to much feeling into this and now I'm hurt. I feel stupid. I have to see him everyday and be reminded that I'm not what he wants and that sucks. I know it's my fault for putting myself in this situation and I knew better but I was so adamant about taking a chance on this. Guess I learned my lesson. 

Now I'm confused though, he texted me to tell me he doesn't regret the choice we made and that he will forever cherish it. What does that even mean? I'm so conflicted.