Hello,
Such difficulty in passing urine and urinary retention is a common complication of benign prostatic hyperplasia(BPH), although it can also be caused by nerve dysfunction, infection, or medications. You have not mentioned your gender but if you are a male, then I suggest you to get a prostate examination and PSA levels checked by a urologist. Also get your urine examination done.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
First step is to see a urologist. Urine and blood tests will be the first step, most likely. When was the last time you were screened for STD's?