Regular Periods and Spotting on Mirena

I have regular periods with Mirena, which is apparently very rare. Occasionally I get some spotting. I actually have some spotting and some slight slight cramping right now. I ended my period about a week/week and a half ago. What is your experience with this? Normal? Ovarian cyst? Ectopic pregnancy? I am a nervous nelly and am sure nothing is wrong but I wanted to ask your experiences.