Urination problem: can't fully urinate. 58 year old male.?

Prostate enlargement. Other causes possible. However, prostate is likely. Need urology evaluation which will include ultrasound plus exam. Over the counter decongestants and Benadryl (diphenhydramine) make it worse. Need to void frequently and not delay voiding? Sometimes, meds is all you need for now. If it gets worse may need a procedure.
Incomplete emptying. Should see a urologist to get checked for obstruction such as BPH or urethral stricture, or other problems that do not allow the bladder to empty adequately.