What on earth is going on with me?

Lately, even though my eating and exercise habbits have not changed, I have put on weight. I get really dizzy all the time. I can sleep over 12 hours and feel like I need more sleep. I have tried sleeping all different hours, and never feel rested. Also, my back has all the sudden felt like there is a knief in it. My skin has always been a little on the dry side, but now it is dry all over my body and nothing seems to help. Like even now as I am just sittin here, I feel like I am about to faint for no reason! What could I have? Also, boughts of panic and depression keep coming and going through out the day. HELP!