Was on alpha blockers, no pain and no difficulty in urination. now no more on ab for week and i feel discomfort & swelled veins in scrotum+pelvic pain?

Prostatitis? : It sounds you were being treated for prostatitis. Often times this condition is difficult to treat and might take time. Antibiotics might have to be taken for more than 4 weeks, and Alpha blockers for even longer. Beyond that urinary issues related to the prostate gland also respond to over the counter preparations like saw palmetto being taken on a daily basis.