My first I wasn't really sick much at all... until after I went to the doctor and got prenatals. Every day that I took my prenatal I couldn't even drink water, everything came up! Days I didn't take it I wasn't sick at all. I fired my doctor after he told me taking the vitamin was more important than eating and drinking!
After employing a new doctor and discussing it, the new doctor told me just to take Folic Acid and Iron. Every day I took the Folic Acid I got sick again! Ended up I was allergic to synthetic Folic Acid of all things.
My doctor sent me to a nutritionist and I ate 4-5 servings of food naturally high in Folic Acid and Iron every day to compensate. It was great after that.
With my second I already knew about the vitamin thing but I had more morning sickness than the first. I just grazed all day, keeping something in my stomach was the key to not being ill. Got to keep that stomach acid working on something! Any time I actually got an empty stomach was immediate nausea.
My best friend was sick all day long with her second son and it got so bad her doctor gave her a nausea medication used for Chemo patients. She said it worked fabulously... except she never felt like she was going to be ill, she just suddenly got ill. Throwing up was a surprise. In my case I don't think that would work for me but she seemed to be ok with it. She said at least it was just done and she didn't have to think about it for hours before it finally happened.