What Causes Headache After Miscarriage?

I had a miscarriage about 3 weeks ago at 8 weeks pregnant. I had severe hyperemesis gravidarum with potassium levels going so low I was in afib. I ve been getting horrible headaches every afternoon and evening since. Debilitating headaches that don t subside with ibuprofen. I ve been an RN BSN for 6 years and I cannot figure out what is going on and I cannot get any relief.