M.S.
I don't know why this happens to you, but I'm very sorry that it has and does. I had every "normal" symptom known to the doctor without actually having anything wrong. Pregnancy was such an ordeal that I stopped at 2, and would love a 3rd, but dread being so sick and incapacitated for 10 months, plus the c-section recovery.
I think that you might have a lot of problems from getting fixed, you should look up tubal ligation syndrome, and then have your husband get fixed if you really are done. It sounds like you might need to be for your safety and that of your family. A mommy is more important than another sibling in the long run. But, I can't decide for you or tell you what to do.
I will say that I wish you the best, and hope that you find some peace and answers.