Hello and thank you for asking HCM
I understand your concerns and my opinion is as below.
You need to finish the dose of antibiotics. After being diagnosed with UTI and started the treatment ,the body needs a coupe of days to get rid of the infection and most of the symptoms,so its normal to have symptoms at the second day of the treatment.
Mirena coil usually do not cause UTI,and don't affect at all the healing process of your UTI (only if you have a vaginal/
uterine infection,than yes mirenal coil will keep the infection alive)
In your case you can help your body heal with these tips:
-have plenty of liquids, 2-3 liters each day
-cranberry juice would be great.
-rose tea,chamomile tea, 1-2 cups each day
-fresh fruit juice
Ibuprofen for your pain,burning sensation etc.
If you have any other question,please feel free to ask me.
Dr.Endri Katro