Missed period?

I had my daughter june 2017, then got the mirena iud august 2017. Periods have been regular since, ranging from 4-6 days. My last full period was july 11th-16th and I spotted august 8th... my boyfriend and I use no protection other than my iud, I have had light shedding/spotting every couple of days with a pink/brown color. I've also had hot flashes, nausea, diarrhea, but I am also on a low calorie diet whic I started on august 1st. Help! What's going on???