I suggest you talk to the optometrist and ask if there is a therapy for your light sensitivity. Increase exposure to bright light by constantly pushing you into brighter and brighter light may not be appropriate right now. But, you need to make this decision based on what the optometrist says.

I wonder which come first. Do you get a head ache from exposure to light then the continued light makes the head ache worse ?

Or, are there other triggers that cause your head aches ?