Jack,   A few years ago I had some very high PSA's.  After getting a biopsy done I was negative for Cancer.  ROughly 9 weeks after the biopsy I started moderate bleeding that would last 3 to5 days then subside for a few weeks and begin the bleeding cycle again.  It was determined by my urologist that I had a prostate the size of a grapefruit.  Very very large.  My Urologist recommended a procedure called Holmium Lazer procedure BUT only a few Doctors were experts at it.  I searched around and found Dr Das at Jefferson Hospital in Phila.  This was in Sept of 2010.  Your should read up on the Holmium Laser.  It is less invasive that TURP and trims and seals the blood vessels of the prostate while reducing it's size.  The procedure was a complete success.  However, every 4 month's I have urinary bleeding after lifting heavy objects or excerising as in very fast walking...etc.  I also take Plavix, baby aspirin and fish oil for a Heart Stent I had placed in 2009.  I am 56 years old and think the vessels on my prostate might have Prostate Varices (weak veins that can tear) AND the blood thinning meds supports bleeding.  If I have an episode without stopping the Blood thinning meds I can bleed heavy clots for up to 10 days.  Thumb size clots are just average and in one urination I could produce 10 to 15 clots during heavy bleeding.  YOU MUST drink at least 2 liters of water EVERYDAY even when your not bleeding because urine disolves clots!  Also if your on aspirin or fish oil if you start to bleed stop thaking them for about 3 or 4 days.  You will see the bleeding slow down.  Dehydration is ur enemy.  You will bleed more for some reason...AT least I do.  I would suggest you see Dr Das in Philadelphia at Jefferson Hospital if your nearby.