I've had 3 DC and have a non hormonal coil.
I had this inserted in April last year as I did not want a Mierna coil which can cause side effects.
I've had no problems at all with my coil- it's been great. My periods have not been much heavier and although I sometimes get a little more ovultion pain, I can cope with that.
If you are continuing to have problem perhaps consider swapping. As far as I am aware, the non hormonal coil is just as effective. I love my coil - I don't have to worry about contraception and have had no pregnancy scares.
I had 3 kidlets in 3 years and absolutely must have any more for medical reasons so I keep a very very close eye on my periods. So far so good; I come on regularly ( within a day or two) each month.
Have a think about swapping over . It sound like your body isn't that happy with the coil your using and you might do better letting your cycle regulate itself. Even if your periods do become a little heavier, I personally would rather cope with that than all the side effects you're experiencing.
Good luck with it and although I have not had PND as such , I have 3 of 5 and under with no family help, my husband works long hours and to top it all I have to have major surgery the week after because my abdomen has split and my guts have spilled out.
My whole life is childcare, housework and operations it seems and it's so so hard. But have courage- you will, absolutely WILL get through. (smile)