Have you gotten a diagnosis yet?
> A cystoscopy to take a look to see what’s causing the dysuria? UTI, prostatitis, cystitis, something else?
> A colonoscopy to take a look to see what’s going on? Proctitis, hemorrhoids, other rectal injury.

It’s not uncommon to have urethral and/or rectal complications depending on how well/badly the seeds are placed. Did you use a rectal spacer?

I’ve read that, if having pain and burning during urination (dysuria) caused by radiation treatments, once they’ve ruled out a UTI and prostatitis, try these in this order:
> Avoid fruit juice, smoothies, etc. with citric acid.
> Try OTC NSAIDs (Ibuprofen/Alleve/Advil/Naproxin/Motrin).
> Try Prescription NSAIDS (Celebrex)

For more serious issues:
> Try Medrol dose-packs (steroids)
> Finally, try the over-the-counter product called Azo (it’s basically a urinary analgesic);

At the extreme —> If it’s radiation cystitis, could need hyperbaric oxygen therapy.

As always, discuss with your doctor about these remedies first.