I am 8 months pregnant and getting a silent migraine every day this week. Jjust the aura. Hormones?

Yes and no. Headaches at 8 months if new may be a warning sign for pre eclampsia. Check to make sure your BP is normal and you don't have ankle swelling and protein in your urine. This happens more with first pregnancy, let your OB know about your headaches.
Tell to your OBGYN! If you have constant headaches in late pregnancy & it is very important to talk to your obstetrician ! to assure it is not result of height blood pressure or " preeclampsia "=specific serious condition which may complicated late stage of pregnancy! do not delay !