Literally?

I take things too literally. Even though I know this about me it doesn't make it easier to tell when someone is jesting or joking or being sarcastic and when they're being serious. I'm aware of the concept and can understand it, I just have trouble identifying it in real life scenarios.

I may be busy doing something and someone comes by and says "You don't look busy." I don't know how to take this. Do they realize I am, in fact, busy or do they not realize I'm in the middle of something? Some people don't appreciate that you can be "busy" on the computer or some other non-physically exerting task. I don't know how to respond to something like that. I usually respond in a serious nature and then the person says something like  "Geesh, I was just joking" but by then I'm already down the road in my response and it's kind of hard to stop mid-thought and say "Oh, ha ha...you had me going." I'm usually at least mildly agitated by that point regardless.

It would be nice if people gave a cue that they're joking when they say things like that. It's very similar to communicating online or in text messages. Assume I'm not "there" to read your body language or inflections in your voice and give me a little "jk" or ";)" at the end.