First I would guess that you are going to have to set a goal for yourself.
Not the 3 miles you used to do. But even say the 1/2 a mile you can
do before the headache comes on. I would also look into a exercise program
that does things that will help you get into shape without the running exactly.

It also might be that the sun is helping with part of the problem with the
headaches. So you might try different parts of the day. Do say the 1/2 mile
then stop till the evening.

I am trying very hard to get back to my exercising at a gym myself.

Donna