Have you been checking your bp? I had these a week after I gave birth and I have postpartum preeclampsia.
Did you have pre eclampsia or high Blood pressure? I would call your OB and let them know.
Did you have an epidural, and does it happen when you sit up or get up too quickly? I ended up getting a tension headache from my epidural, which I was told should clear up in about 2 weeks, but there's a possibility it wouldn't.
Sounds like a migraine I’ve had them before