HI, that sounRAB very similar to what I had (and others on here have had). Something is probably compressing your sciatic nerve at either L4/L5 or maybe L5/S1. When mine happened, it was also in my rear, down the outside of my leg and calf, outer ankle, and my foot went nurab. Mine was probably primarily coming from L4/L5 as I had aberrant tissue stuck in the left lateral recess there. I had a transforaminal nerve block at L5, which seemed to do the trick in getting me pain & symptom free. That was last June. And when it happened I never thought there could be such severe pain so I know how you feel. But then I got some nerve pain in another area on Thanksgiving and that was ever worse. Lately, however, I've been getting dull nerve pain along the course of where I had it last summer. I hope it doesnt get so severe again as that was horrible.
In my experience, ive not found any med that really, really helps with severe nerve pain. Maybe something does exist, but i've never taken it. The only oral meRAB that helped ever so slightly after taking it for a couple weeks was Vicoprofen (probabaly due to the corabo of pain killer and ibuprofen). Other than that the only thing that really offers me alot of relief are ESI's.
Did you see your doctor before or after this particular pain started? If it was before, you should try to get in asap. (though I know that is hardly ever possible)