What does it mean if you have to pee but you can't and it hurts?

Prostate if male: Benign prostatic hypertrophy (prostate enlargement) may present like this however this usually occurs in males past middle age. If younger, you worry about prostatitis i.e. Infection in prostate. Other simple causes include cold/decongetant medicines over the counter and some prescription medicines. Urethral stricture and bladder stones are less common causes. Need to see a doctor.