Kati, I'm with atari on this - avoid sleeping in Lone Pine (3700 ft) before a dayhike of Whitney. If Gorgonio at 11.5K' nailed you with bad AMS, Whitney could be much worse. The Diamox should help, but acclimating properly will help more. You might also want to consider going on an aspirin regimen of two tablets a day (morning and evening) beginning a couple of days before your hike. ASA helps the blood oxygenate, which is a little trick I learned on this message board last year from a physician who's a member.
Sleeping as high as you can tolerate for at least one night, but preferably two, may be the one best thing you can do immediately prior to a hike like Whitney to help ensure your success. You didn't indicate where you live or when your hike is planned, but based upon your experience with Gorgonio I would strongly suggest you make it a priority to get as high as you can, as often as you can, prior to heading for Lone Pine. If an opportunity exists to camp/sleep high for a couple of weekends before your Whitney trip, try to do so. Given your AMS history at 11K', this should be your primary focus.
My one and only experience with AMS was on Whitney in '09. I had successfully - easily, even, - knocked off 13,000 & 14,000-foot peaks in the past without even an altitude twinge. All of those past experiences had involved sleeping at 7000-8000 feet, however. My first attempt at Whitney had me sleeping in LP because of the logistics of hauling camping gear across the country. Never again - I learned my lesson. 13,000 feet on Whitney is NOT where you want to have an AMS episode, especially if you're by yourself and it's severe.
The good news is that you know what AMS feels like and that you're susceptible. Treat it with a very healthy respect and plan accordingly (as with the Diamox), but don't let the fear of it distract you from the fun of the climb. Just be ready to bail immediately if that mild, background headache gets any worse or other symptoms appear. Best of luck and enjoy the experience!
