My co-worker and I flirted for almost a month, hooked up, and now he is acting like nothing ever happened.

Anonymous
There is a new guy at my work that I started talking to shortly before Christmas. Right before I left for my Christmas vacation he asked me for my number to text me something about another co-worker he had a question on. From there we continued to talk everyday that I was gone through text, and on the phone a couple of times. The first week it was just general chit chat, then starting the second week he asked to call me for the first time and we talked for like an hour. After the phone call, he texted me and said 'Want to know something? I really like talking to you." I told him I felt the same and from there it started to get flirtatious, and he even admitted he had made up an excuse to get my number. Well we kept up the flirting for another 2.5 weeks, then I was finally back at work. The first day back he told him how much he wanted to come into the room I was in and kiss me. We ended up meeting after work for a few minutes and had our first kiss, which led to a little making out for 20 minutes or so. The next day he picked me up in the morning and gave me a ride to work and we exchanged a kiss as he dropped me off. We had plans to go out to dinner that night after work. Throughout the day we kept flirting and both saying how much we were looking forward to going out that night. We ended up getting dinner and had a really good time, lots of laughter and good conversation. After dinner we ended up parking somewhere and got into a pretty heavy make out session, where I eventually gave him a bj. I normally never do that but there was so much sexual tension and excitement between us, I couldn't help it. afterward we kissed a little more, then he drove me home. When I got inside my condo I texted him and told him what a good time I had and he texted back the same. This happened on a Thursday. We were off that weekend, fri - sun so I didn't see him. He texted me first Friday afternoon asking what was up and we talked a little bit. I attempted to be a little flirty with my texts and he either didn't flirt back or didn't text me for like another two hours and it was a completely different topic. This continued for Sat and Sun. On Monday we were both back at work and he again texted me first and we had general chit chat but no flirting. It was like it was back to how it was before we had that first phone conversation. He didn't even come into the office I work in like he usual does to say hi. The same has happened today, although he did pop in for a second, but again no flirting. I am at SUCH a loss for how a guy can flirt for almost 3.5 weeks, talk about how much he likes me and wants to kiss me and how hot I am, and then we hook up, and NOTHING. He is acting like nothing ever happened at all. I want to confront him SO BAD and ask what is going on but I don't want to seem clingy and/or crazy if that makes sense? For background he is 23 and I am 30. Any guys opinions would be greatly appreciated!
My co-worker and I flirted for almost a month, hooked up, and now he is acting like nothing ever happened.
3 Opinion