I've gotten sick from colds/flu with each pregnancy. I believe is due to the fact that the immune system is compromised as our bodies are busy making a baby and not really taking care of the host like it usually does.

I would definitely seek another opinion, your symptoms seem a little extreme to be just morning sickness and the doctors should be taking it more seriously. Sleep as much as you can and try to keep the fluids up no matter how undesirable they seem. Good on you for making the medical centre doc give you iv fluids.

Good luck with everything.