A friend of mine has two children and three miscarriages. She was horribly sick with every pregnancy, and early on. I don't think she was even a month along when she started getting sick with her first child.
Her sickness was so severe with her second child that she went into the hospital twice for fluids and monitoring. She was on Zofran the whole time for nausea with that pregnancy. She said one day she sat on the floor to read to her daughter, didn't feel like getting up, and lay there until her husband came home from work. That led to the first trip to the hospital, but she was so sick the whole time.