If you check my poems, I tend to have the last stanza break the format, whether by having it be an extra line, having a separated line, or introducing rhyming after not doing it in the other sections.
I think the ending should stick, and making it stand out by rules-breaking in it helps you do so.
You're still missing a line somewhere to end up with 4-4-5 though. Might be worth going for it. I'd put it just before the first "It hurts," as the final line in the second stanza.