I'm no medic but sounds to me like what may have started as allergic reaction or food poisoning has turned into dehydration which is a serious thing. If you're weak, you'll just get weaker. Youneed fluids like now, but if you can't get them down you may need IVs. I've been without insurance and better to get help and ask for social service assistance. Even if you have to pay $10 a month. 8 days is a long time without water. too long. I hope you ask someone to take you to a hospital or free med clinic. Isn't there a church in your city that offers free medical clinic assistance? Or some churches offer cash assistance for special needs but sounds like you are too dehydrated to do the work to call. Have a friend take you ASAP, please.
Londres70'd advice seconded.
In the United States all hospitals receiving federal aide must treat and evaluate you in an emergency regardless of the ability to pay. You qualify.
Sounds like food poisoning or an allergic reaction related to the crab.
After 8 days, I would recommend seeking medical attention ASAP. I know you have no insurance, but if this has not resolved by now I would be HIGHLY concerned.