Sounds like my first one day to Whitney hike. If you sleep too high the first night you never sleep good. My first 1 day Whitney hike we arrived early at the portal and stayed there that night. Above trail camp the headache came on and it was rough. Felt much better on the way down. The second time we did whitney in one day we spent 2 nights at the portal and it was better. The third time we spent three nights high and we had hardly any trouble getting to the top. I once drove from sea level to white mountain trailhead at 12000 feet and couldn't sleep at all....I could really feel the altitude. I think if you have the time spend the first night a little lower (Lone pine campsight) just to sleep better. Then spend two nights at the portal with a short hike up to Lone pine lake. Or spend nights 2 - 3 up at 10000 feet at Horse shoe meadows. Diamox might be OK, but has some side effects. It made my feet tingle but I thought it delayed real problems with the altitude when I just went for a peak after one night at the portal.
