A.R.
I also have the Mirena and found that it took my body a long time to adjust to it. I started getting more regular with my period at eight months and also notice that I can be very hormonal a few days before my period starts. Also, my acne is worse now which really sucks. I have had it a year now and I love the fact that I don't have to take a pill every day but I wish I had less side effects. Another thing to add is that I had spotting at random times too that seemed like I was having a period. You may see in a few months it start to even out and regulate. I know now that I am on a 28 day cycle and can more predict the mood swings. I have made it clear to my husband too and have noted it on the calendar so he knows and maybe he can help me keep track of any changes.
Good Luck and I hope that helps
A.