Hi Paul: The same thing happened to me at four weeks after surgery -- but for only one day. At the time, no one here in this forum had heard of it either.
I'd had the occasional dark blood and tiny scabs in my urine for two weeks after surgery, then no bleeding at all for two weeks. Then at week four, one day after lunch, I noticed some very bright red blood in my urine and as the day went into evening, my urine was running like Cherry Kool-Aid.
I called City of Hope and the triage nurse said it was "Somewhat unusual, but not uncommon." She told me I had probably “overdone something” physically and that I should take it easy; drink lots of water and keep them informed. She also told me to go to my local ER if I found myself unable to urinate. (In the meantime, she contacted my surgeon.)
about a half hour later, I had the urge to urinate again and when I tried to go, I felt clogged for a second-or-so, which scared the hell out of me. As I stood and waited, clots like you're describing began to shoot out of me -- about six of them -- some with such force that they missed the bowl, hitting the wall, floor etc. The largest was about the diameter of a dime.
Right after that, I had clear urine, which has been clear ever since. I was on the phone twice that night with my surgeon and he said he was a little concerned about this happening at four weeks. He was glad to hear I was running clear urine, but hooked me up with a urologist on call here in Vegas, in case I needed to go to an ER that night.
Anyway, to reiterate, after my clots came out, my urine ran clear and has ever since. But If you've been passing clots for three days I say see your doc as soon as possible. You probably just need an adjustment in the meds you may be taking or need to curtail your level of physical activity in some way.
Hang in there bro,