Caffeine withdrawal headaches are common, and many headache remedies contained caffeine. So taking in caffeine would sometimes alleviate the headache temporarily, then as the levels fell off the headache would recur with a vengeance--a vicious cycle. I don't know about aspartame.
Well the funny/weird part is, I didn't actually have headaches after I cut down on the caffeine and aspartame intake. I had gotten headaches MANY times while drinking and consuming tons of caffeine/aspartame.
I actually had an MRI done, per my mom's instructions, when I was 20 I believe, but they never found anything.... which is good though!
But yeah, I'm happy that I don't have to pop a bunch of pain pills 4, 5 or 6 times a week because of the amount of aspartame in my body.
I actually just read somewhere that 80% of headaches are caused by a food allergen (which both aspartame and caffeine can be) reaction, and most people never know.