I think depression can change in how sever or how it comes about and how long it stays. I think you can be depressed without knowing you are because depression is all about slowness. If you know what depression feels like in your experiences and then you try and compare it to another time you were depressed, ask yourself were they the same?

I was depressed severely for 2 months, at my worst, because I couldn't get out of bed and do anything. I was STUCK. Now, I am depressed, but im not stuck, im social, working, but tired than normal and feeling alittle slow. I think one can be tired physically and depressed but not physically depressed because depression affects your brain, and maybe it is telling you your body is tired.

Has anything happened recently to make you feel different? The smallest things can trigger depression, but they have to be significant or traumatizing to you for your body to react.