Feeling sick on and off for a week. stomach aches and lower back pain. feeling full easily and frequent need to urinate. what could this be?

Suspect Urinary infe: You may have bladder infection(also called Cystitis). You should go see a doctor and get your urine examined(urinalysis). If the urine showed pus cells or bacteria a course of antibiotics may be prescribed. This would very likely take care of your problem.

Possible infection: Your symptoms could be due to a kidney or bladder infection, so you should see a doctor as soon as possible to have a urinalysis. This is a simple test, just be aware that they need a urine sample, so don't go to the restroom just before your appointment! :). Kidney infections can be serious, so don't delay any longer. There are other possible causes, but the first thing to rule out is infection!