Could I be depressed unknowingly?

I've been baseline and low for the last week. Today, I've noticed that I'm unsociable. I've been very content just sitting in the dark, with the tv on in the background playing a single player game online. For the past week i've been excessively sleepy but the two weeks before that I was completely unable to sleep. I'm going from not hungry to starving at random times (woke up at two am starving, then spent most of today not eating, and then ended up 'starving' again and was eating cereal/chinese food at the same time and now I don't even want to look at food - and no i'm not pregnant.)

When I saw T last week, it was a "low day" and she could pick up on it, but i've had some pretty baseline days too (probably twice as many than low). T pointed out that I had been unsociable, (not with the intention of being antisocial just not thinking about contacting anyone). She suggested that i'm just 'doing what depressed people do'...which would make sense except, I don't feel 'emotionally' depressed.

So I was wondering, is there something with my health that I need to be looking at/making appt. with my GP for or am I just stuck in a depressed pattern without realizing it? Can one just be 'physically' depressed?