Only YOU can tell if the hearing aid is too loud or too quiet.
The audi have no way of knowing that - he or she can approximate what is the most optimal sound level for you, and that's that.
But since it's YOUR ears, YOUR hearing only YOU can be the judge of how loud is too loud or how bass-y the tone should be or how trebble-y.
My audi thought since in a way I can hear 'better' higher frequencies it makes sense to increase the trebles for me.
It was a absolute disaster experience for me. Everything sounded "metallic, tinny" and one sided - I hated that.
I demanded to increase the bass instead, as it balanced the trebles for MY personal hearing need,
then asked to increase the loudness overall,
particularly in my new digital Siemens as much as possible without causing it to whistle (feedback).
So much better.
Your headache might be caused by number of things.
It's most likely possible the loudness is set too high.
Or, like it my case, too much treble, or bass.
Perhaps try different bass/treble balance just to see what YOU like best.
Mind you, these fittings take HOURS and a lot of patience on your part.
If you are prone to migraine, even such a seemingly irrelevant detail like poorly fitted earmold or a pulling hook/tubing may trigger a headache since it may cause pressure on the muscles and these in turns on the nerves in/around the ear.
A detail without much significance to a regular person, but for someone with migraine important, as migraineurs are extremely sensitive to any external stimuli.
Even an innocent necklace may trigger a headache.
It's also possible you are simply not used to to being bombarded with so much sound for so long yet.
Try to remove your hearing aid during the day - take breaks, and see what happens.
Fuzzy