curls very sorry you are here and feeling so low, but congratulations on your pregnancy. Also so sorry to read you had a mmc - but the positive news is the increased nausea and vomiting is an extremely good sign that the hormone levels are rising and the body's doing what it needs to in order to sustain the pregnancy.
Excessive nausea in pregnancy is just as debilitating as the vomiting, if not worse. It is most definitely part of HG. There is medication available for you to take which can reduce the severity, and I would recommend going for a chat with your GP anyway to talk it through. Malnutrition can be just as serious as dehydration.
You sound pretty severe to me! The peak is exactly as you describe, and I think most of us found it at its worst around week 9. For some, it will tail off by the 12 week point, for some it will continue till about the mid-second trimester and/or return later in the third (that's me) and for a poor few it lasts the whole pregnancy.
I know many of us have struggled with the pregnancy and the sickness, wondering how on earth we can continue. I've spent the best part of pregnancy moving between the bed and the sofa. The best thing to do is sleep and rest - get signed off work as overdoing it can make it worse, and support from your OH in looking after your DD will mean you can rest up more. Others who have gone through this with kids will be online soon to share their advice, but for me it is just rest, rest, rest. And don't feel guilty. HG is an illness as a result of pregnancy and nothing to feel bad about.
As for what helps - sipping icy cold drinks through a straw was awesome for me, diet coke is still my go-to cure (tap from McDonald's though, nothing else), and I went through a phase of frozen Orange Capri-Sun. Food-wise, Nutella on toast was about it and it had to be white bread. That has been my main staple in pregnancy because I found that the foods I could tolerate rotated every couple of weeks or so. Sucking on sweets helps some, or flat full-fat coke.
Non-scented 
for you.
elizabeth 
how did you survive the end of your pregnancy with that! Carrying twins is a feat in itself, let alone with HG then a stomach bug!
I LOVE chocolate milkshakes from McDonald's but alas the sugar in them makes me feel so unwell. I suppose it's a good thing really 