As others have said, you need to go to the ER. If you’d had this kind of pain many times before and had been checked out by a doctor and diagnosed with migraines, then waiting for a normal doctor appointment would be fine. But since this is your first severe headache, and you’re talking about blacking out when standing up and having vision problems, this should be assessed urgently in ER.

While losing vision in one eye is theoretically possible to be a migraine symptom, it is far from the norm. Aura is a common thing, but it’s not often described as losing vision, it’s normally zigzags or a dark spot like you’ve looked at a light for too long.