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 :(.

caffein does relieve most headaches to some extent. But, of course, it`s effect is weak when compared with real pain relieving medicines.
The wast majority of headaches are not caused by migraine, but are usually of the "tension neck" type.
Anybody suffering from bad, chronic headaches should see a doctor to make certain that it is not a warning sign of something more dangerous (it usually isn`t).
1000 mg acetaminophen is the safest and relatively effective drug choice for most bad headaches. The second choice would be some non-steroidal anti-imflammatory drug, for example 800 mg ibuprofein. (always remember to read and follow the drug`s safety instructions)
100 mg of caffein (1 tablet or 1 cup of coffee) may boost the pain-relieving effect of those drugs a bit, might be worth trying out.
If those dozes don`t help see a doctor...there are
very effective, although reletively expensive,prescription drugs for migraine type headaches.