11 week postpartum

I'm currently 11 weeks postpartum. I've been having horrible nausea, headaches, and dizziness the last 2-3 days. I starting bleeding earlier today and now I'm having *horrible* cramps. This is nothing like my pp period after my 1st born or before I had children. I did take a pregnancy test today and it was negative. Could this be a miscarriage? 💔

Edit to add: We did have sex 3 days before I ovulated - not knowing I was going to ovulate as normally I have *very* consistent signs 3-4 days before. 😬