Guys/Boys what does this mean!!!Help!!!?

[Niki]

I really like this guy and everyone says that he likes me too. We spoke on Facebook for hours the other day but today I asked him about a due date for an essay. He told me about the essay and we spoke some more (he sent me a kiss even though I didn't) and then I said to him that I should be doing my work but I'm talking to him (I made it into a joke) and he replies with 'Sorry, you keep replying, why don't you just stop x'. This thing has been going on for 3 months now and it feels like we're more than friends but less than a couple. Guys/boys I found what he said quite harsh as if he's saying 'I'm only speaking to you to be polite' but what do you think it means? Should I or should I not be upset?
Thanks for any answers, I appreciate it