I used to (the last several years) over eat and sleep all the time, but these last few weeks I'm hardly eating at all (once every day or two) and not sleeping for 3 days at a time. I used to have no energy and could stare at the ceiling all day, now I am still tired all the time but extremely restless and can't sit still. I am not undergoing any treatment or taking meds at this time. why would symptoms flip like that?

Possibly bipolar disease – manic depression?

because depression isn't a stable thing it changes over time unless it is treated get help

Are you showing any other signs, like shopping to much are just doing things out of the ordinary? You could be Manic Depressive. I would see a specialist and get on some meds.

Could be something like a hormonal or chemical change, or a change in your enviroment. Depression is such a strange illness. if you have experienced such a strong change in symptons, you really should seek outside help.

You need to hook up with a mental health clinic.

For one, depression is due to an imbalance in brain chemistry, so if you're not on meds, it's not going to get better.

If you can't find anything in the phone book, call 1-800-SUICIDE and they'll hook you up with local resources.

Why do people see depression as an illness. Can't it be just how you feel? That's what is wrong with today's society, "just pop a pill in your mouth and everything will be o.k.. I just don't get depression. I am depressed but I see the only cure being myself. I have to take control of my life and try to become happier. what if that chemical imbalance is set off by your thoughts? just think positive and it will go away.

Please see your physician as soon as possible. i wonder if you have an endocrine problem such as your thyroid could be off kelter. Go this route first.
Good luck.