Update: No more headaches; riding 5 to 6 days a week. Here's what I've changed so far:

1. Switched my glasses for some with a wider lens and thinner arms.
2. Putting NUUN in one of my water bottles.
3. Stopping every 30 minutes to drink regardless of thirst or no thirst.

Still trying on helmets everywhere I go to see if something fits better. Nothing so far.

K.