Have you ever tried the modern migrane drugs? As I don`t live in the USA I don`t know their trade names over there, but any doctor would know what you mean if you asked if he/she thinks the TRIPTANS (eg. sumatriptan, rizatriptan) would be suitable for treating your headache.
They are very effective and safe, but work only for migraine type of headaches.
Scarlet`s allergies would most probably not be a problem because the triptans are totally different
kind of drugs than asperin, NSAIDs or opioids (eg. codeine). And have you tried acetaminophen? Your asperin/NSAID/codeine allergies do not prevent you from using acetaminophen which should always be the first drug to try for all headaches. And it is cheap too :).
Maybe the only bad thing about the triptans is that they are quite expensive :(.