You've got my sympathy. I'm 30 weeks now with a boy and had AWFUL all day sickness, retching and throwing up between weeks 6 and 16, then slightly better from week 16 to 20. Since that time, if I get stressed, tired, hungry, drink caffeine, or eat or smell certain foods, I feel sick and sometimes throw up - but it's nothing like as bad as my weeks 6-16 where I actually thought I was dying. Like you I also thought I would never want to go through pregnancy again. Now, at week 30, I have changed my mind and think I could do it again. I am actually starting to forget how horrible it was when the sickness was so bad and focus on baby's movements and decorating nursery etc, which i wouldn't have had strength to do earlier in my pregnancy.
Things I did when it was at its worst were: lying down and trying to sleep as much as possible (being horizontal seemed to help), drinking and eating anything I felt like, not what other people wanted to eat! I could keep down yoghurts, cereals, baked potatoes, crumpets, toast and jam, rice pudding - really plain, carby foods. I also had a thing about citrus - orange juice, oranges, grapefruit, etc, oh, and cheese. It's different for everyone the kinds of things people feel like having. Garlic, onions, olives, cooked meat, cat food - all these things were my biggest "triggers" and would make me throw up as soon as I smelt them. It's good to work out what triggers your sickness and avoid those things like the plague until you start to feel better.
I went to my GP and got prescribed some pills too - Cyclizine and Metoclopramide. They mainly made me sleepy, only helping the nausea a bit. But they were better than nothing. I was assured they've been safety tested and all my scans and tests etc have been fine since.
I also found that getting out and going for a gentle walk helped my sickness (avoiding foody places like restaurants, supermarkets etc! Somewhere with fresh air like the seaside, lakes and parks etc). The exercise seemed to really help whilst I was doing it. As soon as I stopped the sickness would come back on again though sadly. Being busy and distracted also helped a little.
Oh yeah, and over all I had to have about 15 weeks signed off work by the doctor during my pregnancy. I just couldn't have done my job while needing to run off to the toilet at unpredictable times and feeling so distracted by constant nausea. I felt a bit bad about all that time off but honestly, you just know when you cross that line and are too sick to work.
Trying to be positive here, like labour pain, you WILL get through this sickness and you WILL one day forget about how bad it was. I am already starting slowly to forget how awful week 6-16 were for me personally. I still get some sickness on and off but I can totally cope now and know it will pass if I use my coping strategies above (lying down, small snack or drink, avoid caffeine and trigger foods, go for a walk, distract self etc, take sickness tablet). There are also lots of things to "keep you going" when you get further along in your pregnancy like feeling baby kick - I love it when he kicks and I love putting bio oil on my tummy at night too. It's helped me bond with baby where earlier in my pregnancy I have to admit I was really resenting being pregnant at times!
It will all be worth it in the long run.
Hope you feel better soon. Remember it's different for everyone but they say for the average woman things start getting better towards the end of the first trimester, so about week 12ish.