*hugs* Hi sweetie .. I'm so sorry you're hurting so much this week! :(
Actually the only time I've really had something like you're describing (where the only way I could relieve the pain was laying flat down) was when I had LOW pressure, for about a week following a lumbar puncture. Have you recently had an LP, or could your pressure be low for some reason?
I do have typical IIH headaches sometimes where it gets to the point that the only way I can relieve them is to basically lay down and rest till they let up ... but they don't generally come right back as soon as I try to walk, drive, etc. Maybe some others here will have some experience to share.
Hang in there, sweetie! Have you called your neuro about this pain?