You should defintiely go to the doctor and have a blood test done. I took two home tests and had to specifically ask for a blood test at my Dr. It may be that your hormones just don't read on the home tests, especially if that's how it happened before. All the symptoms you're describing sound like you could be pregnant, even if it's not the same as when you were preggos before. My grandmother told me she was sick as a dog with my dad, but wasn't sick at all with my uncle. Even though you're the same person, your pregnancies can be totally different.
I hope things turn out the way you want them to. It sounds like you don't want to be pregnant again, but I also hope you are not seriously ill! See a DR. at once!