How frequently were you taking it? How many grams? I limit myself to a MAXIMUM of once per week and never more than 5 grams. When I first started using it I would use it every couple days and when I ran out I experienced the depression and inability to sleep, hence why I limit myself so much now. It only lasted a few days for me.
I've heard of many people having similar withdrawals as you and most seem to agree that it only lasts about a week, possibly a bit longer. I would say you should start feeling better in about 3 or 4 days at most. Just hang in there. You'll be fine.