How many chemos have you done so far? Did they give you Neulasta? Light headed and pouring sweat may be an electrolyte imbalance too, I would eat some salty foods.
Whatever it is, if this lasts til the morning or starts getting worse you call the doctor ASAP.
PS, I only say that about the electrolyte imbalance because I tend to get those symptoms during the summer. I don't add salt to anything and in the summer I try to drink plenty of water, which can throw your body off. I take a couple of salt tablets everyday in the summer.
But that is only a guess, if you get worse, call the doctor or go to the ER.