Did I screw up?

I need an advice- I'm married and need an advice on what happened between a male coworker and myself. Last week, our team went out for drinks.
One of my male coworkers and I ended up spending the whole time talking and just having a great time. This wasn't the first time we went out as a group and prior to that him and I were always friendly and supportive when it came to work stuff. That night, however, his friends from outside of work joined us and we stay until partying until early morning. Him and I spent the whole night talking and he told me a lot about himself. I found out that he has some girlfriend problems and he shared intimate details from his private life, etc.
Couple days later, he texted me and said that he had a great time and he would like to do get together more often. I replied that I would like that too.
He said that his friends liked me too and they had a great time as well. Over the next few days, we texted a lot, just talking about silly stuff, like movies we like, and what we do for fun. Our texts were friendly, maybe even a bit flirtatious but I didn't think I was doing anything wrong. I figured it would be fun to have a male friend with whom I can talk and go out for drinks.
Then all of a sudden yesterday, he started acting very awkward at work. He was avoiding me and I when I tried to have a conversation such as : what are up to?, he acted like was trying to distance himself from me.
His tone was completely different and made a point of mentioning that he's meeting his girlfriend and that he has to hurry home right after work.

So here is my question- what really happened? Why the sudden change? Was it silly of me to assume that men and women could be friends?
Did I cross the line by texting and having a good time? Does he think I'm a horrible person for being friendly with him while being married? Did he realize it's pointless to continue our talks?
I want to know what guys out there think. Should I just forget him and stop thinking that we could be friends?

The sharing of intimate details and flirting with someone of the opposite sex while in a relationship is generally considered unacceptable by the partner. Having a laugh with people of the opposite sex while in a group is one thing, but it's the intimacy the two of you were creating which was the issue. In short, this sounds very much like the two of you were embarking on an emotional affair.

Anyway, I'm going to suggest that he's pulled back because he's recognised that the two of you were getting too close. Either that, or his girlfriend kicked him up the arse.

Out of curiosity, was your husband fine with the two of you sharing intimacies and flirting? Or did you not tell him those details? If you didn't tell him, it's because you know in your gut that the two of you crossed the line.

I think that possibly his relationship problems have made him gravitate to you as a female with whom he can have fun and a simple relationship. Maybe he does like you romantically tho so be careful. As a male with very few female friends I'd say it's difficult to have female friends, if they are anywhere near attractive I develop more than friendship feelings towards them, even if I don't want to! Maybe he's worked out he really wants to work on his relationship and concentrate on that and closeness with you might confuse him.

Ps if you've been flirty then don't let your husband see, if that was my wife I'd go ape, friends if fine but flirty is crossing a line in texts etc

Thank you for your thoughtful responses. I agree with both of you. I know that he's trying to work on the relationship with his girlfriend so probably thought that our friendship might get in the way.
So here comes my next question- what do I do now?
Do I act like everything is still the same and continue being friendly minus the flirting, of course, OR do I take a hint and back away?
Truth be told, I don't want to back off because we have a lot in common and could be good platonic friends. Is it even possible? If he finds me attractive, is it possible for us to be friends?
Also,I feel that if I back away, it might be an admission of guilt am I reading too much into this?
What do you guys think?
P.S. My husband doesn't know that about the flirtatious texts. He knows, however, that I'm friendly with people at work, including this guy.

Get over it for goodness sakes. You are married and I'm sure at your age that you have plenty of friends already that are both men and women. You don't need to be getting yourself onto a slippery slope of being attracted to him and trying to disguise your attraction as a platonic friendship.

Just be professional at work and leave it at that.

Agree with wakeup!