One of the reasons that I did not go with the shorter 5-sessions of radiation was due to the reported higher risk of urinary bother with the higher radiation dose each session (though I did use Tamsulosin throughout my treatments just in case)..
> Flomax (Tamsulosin) will help relax tissues in the bladder and prostate, allowing you to urinate more during the day.
> Limit your fluid intake many hours before bedtime.
> You’re already taking ibuprofen; perhaps a different NSAID (Alleve/Advil/Naproxin/Motrin) will work better for you?
> Consider trying a prescription strength NSAID (Celebrex), perhaps that may work better.
> You should try that prescribed 6-day course of steroids (Medrol dose-packs); that’s supposed to work better than all the others above.

Is there also any pain and burning during urination (dysuria)?