Help!!

I'm a very introvert person and take time to open up to people. Last year my best friend invited me for an outing with a bunch of people that were complete strangers to me. And because I and my best friend are not in the same college we don't associate with the same people. 

Anyway, everybody in the group really liked me and now I'm friends with all of them. I don't want to stretch this into a long story. So few hours ago I was chatting with one of my guy friend from this group. And after the usual formal hi's and how are you? He asked me when does my spring break starts. And I replied that it starts next week. He said his spring break starts next week too (He's in his masters program) So he asked me if I have any plans for the break and I said I will be visiting a couple of friends who lives out of town and I will also meet with my best friend (through whom we met) So he's like "what about me? I'm not included in you plans?" And obviously since he was teasing me I thought I could tease him back and I responded "you're never included in any of plans ever. :-P " To which he replied "ha ha I was kidding." And he sounded a little off to me so I asked him if he's okay? and he's like you know you were a little harsh. 

I don't understand what the hell did I say that made him upset? Any suggestions? :-/

And obviously since he was teasing me I thought I could tease him back and I responded

You: "you're never included in any of plans ever. :-P " 

To which he replied "ha ha I was kidding." 

And he sounded a little off to me so I asked him if he's okay? and he's like you know you were a little harsh. 

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That's just one interaction.. You could have added, oh I knew you were kidding, that's why I was going with the flow, don't take it to your heart. Or something to that effect. Or you could have just said, it's not like your plans have me written all over them either, is it? 😆

It happens all the time, you wanna say something and the other person ends up taking it as something else altogether. 

Thanks for responding. 
 

... He could be wanting you to say something to him now.. or show signs of you being interested in him and that's probably why he's pulled away or is "upset."

If I were you, I would just wait for another interaction with him and even out my earlier "boo boo" there. Or if you're REALLY interested, I'd text him first.