I'm on the mirena (levonorgestrel) for 3 years now and for the past 5 months I've had a regular period accompanied by uti. No burning, just urgency. What's going on?

Not normal. It's okay that you have a regular period on the mirena, (levonorgestrel) but not okay that you have uti. I would definitely discuss with your doctor. Obviously he/she has been treating you for these uti's? Discuss and make sure that there's not another reason for the uti's... Unlikely it's the mirena, (levonorgestrel) but not impossible if it's changing your body's natural flora.