
I was sick with my first pregnancy, but it was bearable. My doctor actually used the term "mild hyperemesis" (there's a joke here somewhere: hyperemesis means extreme vomiting). I threw up a lot, like 5-10 times a day, but I could function. I went to work (and came home and felt sorry for myself), but I could tell you how many times I threw up, I didn't lose weight, and like 70% of all pregnant women, I got through it.
With my second, I started feeling nauseated around 5 weeks. Then, I started throwing up regularly and spitting all the time (I didn't know it at the time, but it's called pytalism), and stopped drinking. Any liquid made me vomit. One night, around 6 weeks, I started vomiting and I felt like I could not stop. I couldn't keep track of how often I puked, I was throwing up so much.
Then, I started getting dizzy (spitting + not drinking = dehydration). I spent a week or more flat on my back in bed. If I turned my head, the room spun and I threw up. I lost about 15 pounds in two weeks or so. If you've had hyperemesis, you know what I'm talking about. If you haven't... well, it's like labor or war, you can try, but you can't really explain it (just so I don't sound like an absolute whiner, I am not equating throwing up with going to war, it's just one of those you have to see it to believe it sort of things - if I had to choose between labor and hyperemesis, I'd choose labor - if I had to choose war or hyperemesis, I'd obviously choose hyperemesis).
With the help of a prescription, I got through the worst of it. Then at 12 weeks, I was walking up some stairs and I felt a sharp pain in my thigh, like a pulled muscle. I thought that was really weird because I had been doing nothing except laying around (and sitting with my legs curled up). For the next few days my leg got increasingly more painful, to the point where I was limping.
Two nights before I found out what was wrong, my leg was in excruciating pain. I felt like the pain was deep in my thigh (and groin) and I could not figure out what was wrong.
I threw up. I got up to clean out my bucket and threw up again in the kitchen. I kneeled down in the middle of the floor, threw up again and just started bawling. My leg hurt so badly, I was still throwing up so much, and I was just so tired of being sick. I didn't want to bother my husband (what could he do?) and I just felt so awful and alone.

In the morning my entire left leg was red and swollen, so I knew something was really wrong. It was Sunday. We talked to Ask-a-Nurse, looked some things up online and it seemed like maybe I had a DVT (a blood clot). The nurse said that blood clots always got progressively worse, and my leg was not as painful as it was the night before, so I thought, it can't be this. Plus, blood clots can be fatal, so it just can't be that.

I went to the doctor Monday morning and had an ultrasound. They found a huge blood clot that went from the middle of my thigh to my groin - perhaps higher, they couldn't see where it stopped. The DVT was most likely the result of being dehydrated, immobile, and pregnant (a pregnant woman is hypercoagulable - in other words, her blood clots about 5x faster).
I was admitted to the hospital for a week and put on heparin (a blood thinner). I gave myself injections of heparin twice a day for the rest of my pregnancy.

The happy ending is a beautiful girl who is worth all of it.
If you have hyperemesis, you should check out hyperemesis.org. Emedicine.com also has some helpful articles.