Hi, I've Never Written To Anything Like His Before, So

Hi,
I've never written to anything like his before, so hopefully you can help me?
I had the mirena inserted 6 months ago, and have pretty much had my period the whole time. It sometimes stops for 2-3 days every few weeks. I can't afford to go see the doctor who placed it for me, so I went to the free clinic today and she gave me a script for the pill. I had never seen this doctor before, and I didn't really understand what would happen. Is it safe for me to take the pill while the mirena is inserted? Will this regulate my period after the first month or will I have to take the pill forever? I just can't find any information on Google. I previously used the pill for 10 years and had horrible side effects (with moods) which I wasn't aware of until I actually stopped taking it. That is why I had the mirena inserted after I had my baby as I didn't want to be on the pill again. I just don't know what is going to happen. But I'm desperate for my period to be normal.
Any information you could provide would be helpful.
Thankyou