Firstly OP, I hope you're in A&E and being treated.
The level of ignorance on here astounds me sometimes.
Never ever tell somebody who's suffering severe diarrhoea and/or sickness to drink as much water as possible, all you're going to do is flush out the salts that your body is trying to hold on to. Small sips of water/diarolyte.
Imodium isn't going to work when the symptoms are this bad.
I've had norovirus, I felt so poorly but I wasn't losing blood or unable to lay down because of pain.
As soon as you start losing blood whilst going to the toilet, you need medical advice. Not the odd smear on tissue where you could have possibly irritated from wiping a lot, but full on blood in your stools is seen as a medical emergency.
Hospitals don't want people in with norovirus because of how it spreads however, if this is a very extreme case of it, the OP will need hydration drips and painkillers.
Personally, I don't think the symptoms match with norovirus and I would be inclined to think you've got food poisoning which can be very dangerous.
Hope you get treated and feel better soon, as for your partner, he sounds like an absolute tosser.