IUD with no period, now I have PMS

I've had the Mirena IUD for about 4 years now and I absolutely love it! I haven't had a period and I've had 0 PMS symptoms. I moved in with another girl 4 months ago and the past two months have been dealing with serious irritability, cramping, bloating, etc. could this be PMS? She's about to start so I'm wondering if our cycles are kind of syncing but I'm not getting the actual period. This is MISERABLE! Help!!