Thank you all so much for your advice. I decided to go with a Naturepedic
http://www.naturepedic.com/. My mom drove me to a showroom that was wheelchair accessible and I was able to try them out. The ones with latex smell really bothered me, plus I am sensitive to it in general, so I didn't want to take the risk. So the one I chose is constructed like a traditional coil mattress with organic cotton and wool. Naturepedics are pricey, but they offer a 20 year warranty and given I don't go to movies, haven't been to a restaurant in over a year, etc., I figure I've earned this in social life savings.
I know investing in an organic mattress is the absolute right decision. I have been camping in my living room for a few nights and so many of my sick symptoms have diminished or gone away completely. Fatigue is always there of course, but at least my migraines, joint pain, ear pain, diarrhea, face burning, eye swelling, feeling drugged all the time and nausea have gone down. My asthma has also improved, but that could be the weather. I firmly believe the memory foam topper is primarily to blame, which is a shame because I love love loved the way it feels. Interestingly, my symptoms escalated when I bought my first topper over 4 years ago. I'm thinking this is not a coincidence.
Something else I learned, if you can't afford organic furniture and you are worried about out gassing, gently used leather furniture ain't a bad way to go, given it's relatively non permeable, easy to clean