Erratic cycle

I'm now 10months postnatal and I'm still breastfeeding around x6-10 times a day. Period came back at 5months when I had my copper IUD fitted. I didn't go back to have it checked as baby was I'll and I'm not overly worried if I was to get pregnant again.

So since periods returned I've had some intermenstral bleeding until this cycle the period came 4days early and essentially lasted two weeks as I had period one day no bleeding then heavy spotting for another week! Spoke to Dr they offered meds but weren't worried and said to monitor. Now my period was due 3 days ago and nothing so far, pregnancy test is negative.

Wtf is going on, is it the breastfeeding, the iud or is it something else. I'll give it a week and speak to Dr if I still don't have a period and test still negative. I was like clockwork before I had a baby and I had an IUD then too