Ms, is hard! Especially if a) you have other littlies to care for (so can't just rest/take yourself to bed) b) have to work (ditto) or c) feel constantly, drainingly nauseaous rather than the 'Oh, I feel sick' 'I feel much better!' or even for it to be the 'classic type - feels sick upon waking but it's abated but eating.
Pah. Even worse if those around you aren't sensitive/sympathetic to how debilitating it can be.
I LOST two stone when pregnant with DD - I was only 9 1/2 stone to start (5' 7") so didn't have it to lose... I was young and inexperienced and just put up with it (thank god she was my first so I did spend a lot of time in bed). Looking back, I had hypermesis - I would have been medicalised or hospitalised these days, I expect but back then (she's nearly 17) not so much (especially as I was meek and not telling anyone how awful it was).
DS1 I had one brief moment of feeling sick when on a bus - so take heart that not all pregnancies are the same, even in the same person (though I doubt you're planning dc3 right now!)
DS2, 3 and this one, 4 followed a similar pattern, to a varying degree, but lots of feeling crushingly sick until 14-16 weeks.
Once you've tried all the 'top tips' for warding off nausea, the only way to get through it is remind yourself constantly that it will end. Even IF it's delivery, even if you're one of the very unlucky ones, it DOES end. And as long as you at least stay hydrated the baby will be absolutely fine (DD was a robust 7lb 13oz - I was skin and bone!). Eat when you can.
have you tried ginger I jest! 
Sorry. I know it's grim. But you can do this, really you can. There are support threads here on MN for hypermesis too that may help you when things seems particularly bleak? Either in a 'get tips you haven't tried' way or in a 'well, there are others have it worse than me' way.
Hang in there - potentially you're at the cusp of it really getting much better soon. THe few 'better' days would be a hopeful indication of that.