Period on IUD after a year

I’ve had my mirena IUD for a year now. My periods stopped altogether about 6 months ago, and I’ve had a bit of spotting here and there when I’m ovulating or due for a period. Yesterday I got an actual period, it’s still here today. I had cramps too (nothing unbearable) and really sore nipples last week. I took a pregnancy test and it’s negative thank god, but I was just wondering if anyone has experienced anything similar?

My doctor said when I got it put in, that it’s more alarming for a period to come back than to go away with the mirena. So I’m a bit worried it could be something else. Help please? I can’t get to the doctor until next week