Hi Heartbeep
You do not have to ride it out.
You have Hyperemisis Gravidarum (aka HG or just Hyperemisis). I've had it twice, in both pg. I feel your pain, it is absolutely awful.
Firstly, ring in sick. You can self certify (and say something innocuous like "stomach bug") for a week. It may help if you tell your line manager that you are pg, but tell them to be discrete. Mine knew before anyone, but was sworn to secrecy to everyone except HR.
Get as much help as you can with your older child. My mother in law came up to look after DS (then 2.5) when I was ill in second pg, last year. When it became obvious HG wasn't going away any time soon, we used our savings to put him in nursery full time (he was there 3 days a week anyway). I got signed off work and just lay, pathetically, in bed.
Go and see your GP too, explain everything you have said in your OP and ask about the possibility of 1 - anti sickness meds and 2 - being signed off work. There are a few antisickness meds (anti emetics), and none of them is a dream ticket to normality, but with trial and error you may find one that helps you. Beware, some GPs are not sympathetic to HG and some may not prescribe anti emetics (our practice has a GP old enough to remember Thalidomide). There is also a consultant in a hospital near me who believes that HG is all in the mind. If you haven't done so, now is the time to send off for your NHS maternity exemption cert.
If you get very dehydrated (dark wee), then you really need to go to hospital to be rehydrated by drip. They'll deal with the dehydration, and try and stabilise you with anti emetics. I always found the IV ones in hospital far more effective than the tablets from the GP. You can go straight to A&E, who will admit you if necessary. I have done this, and also been referred by my GP.
My hospital (Barnsley) also gave me an early scan both times to see if I was having twins (more hormones, more likely to make you sick).
The good news - your baby is not at risk, especially if you get on top of the hydration. Could you try melting ice cubes in your mouth? (I did this a bit). At one point my wee was the colour of well stewed tea, and DD is fine.
The bad news - it could go on for weeks. With me, it cleared up at 14 weeks in both pg, but there are other ladies out there still suffering at 40 weeks.
Have a look here too, the website has really matured since I was last pg last year. May be worth genning up on the "Heathcare Professionals" bit, in case you need to "educate" your GP.
There is also a lovely HG support thread on here, to moan, rant and share coping tips.
HG is the main reason why I will not be having any more DC (I have 2, DD is 4 months old; DS is 3.5). The things that I tried included:
Toast and Marmite - helped a little in early days
Mini Cheddars - ditto
Melting ice cubes in mouth - prolonged one of my many trips to hospital by a day or so
Accupuncture - Waste of time and money
Sleep - OK, I only once ever woke up to be sick.
Ginger biscuits, travel bands and all that jazz - Absolutely pointless
Drugs - Cyclizine OK, Ondanestron/Zofran - Good, IV Cyclizine in hospital - brillant, but with mega trippy side effects , metaclopromide worked in first pg, but not second; Avomine (also sold as "Joy Rides" for travel sickness) made me worse. Phenergan kept my friend out of hospital for her whole 2nd pg.
I hope you see this post soon, and I hope you can get some time off work and rest, see your GP. I was really scared of going to hospital, but once I'd surrendered to the reality of how ill I was, it was a relief to be there, amongst people who would look after me. I also took great pleasure in throwing up on the (apparently) 12 year old male doc who told me I really needed to pull myself together.
I am thinking of you Heartbeep, you have all my unMNy hugs. It is a horrible, horrible illness, but the end result is lovely!