Can Alpha Blockers Be Taken For Rectal Pain Due To Prostatitis?

I have vaguely been diagnosed with protastitis by my urologist (seems more like a guess than knowledge) due to frequency of urination, etc. (including pain in my glans penis following surgery in that area) and was prescribed Pamsvax XL alpha-blockers. I took these only briefly since they seemed to make little difference and in view of possible side effects (including rapid heartbeat since I have arrythmia and experienced no ejaculation when taking the tablets). However, I now experience increasingly regular sharp stabbing pains inside my rectum where I assume the prostate to be, which worries me as well as being extremely painful. Will the alpha-blockers help to relieve this and are they OK to take with my existing medication (Sotalol, Simvastatin & Warfarin, as well as B12 and zinc tablets)? I am also worried that the urologist does not know for sure if it is prostate cancer (they guess not due to low PSA). I have been told that only a biopsy could check this (unreliably) but I have read recently that the use of powerful MRI scans could avoid any such intrusive procedure - is this yet available?