I have my uti for 3days and i'm still in pain?

See your doc: You need a urine culture and further diagnostics to make sure you are receiving the right trreatment.

May take up to 7 day: Antibiotics, if effective, often clear the bladder of bacteria very quickly because they're concentrated in the urine. However, the inflammation (irritation) of the bladder walls may take days to resolve and the symptoms like burning with urination, frequent voiding, and pain. If these persist beyond one week or high fever or flank pain develops then contact your doctor.

Cause not addressed: See your doctor - if an antibiotic doesn't relieve your pain within 24 hours, it may be due to the bacteria being resistant to it and another antibiotic needs to be prescribed, or else the original diagnosis of a UTI needs to be revised- your pain on urination (dysuria) may be caused by something else.