Cath {{{hugs}}} I know this is a very tiring time for you as well.
Calum has just got over another chest infection, his milk dropped to about 6oz per day (still no nightfeeds) and we were lucky if he could keep that down. He was projectile vomitting every where and I had to stop his solids a few days then slowly give him runny pureed soup and some mil and watery juice to keep fluids in him. He has little wet nappies and his fontanel will sunken, so I just kept offering him water.
If you know he is ill I wouldn't be concerned about a lack of apatite, Calum went 6 or 7 days with little milk and food, now I am glad to say his appetite has return with avengance and he is taking loads more than before he was sick (both milk & solids).
If you are in anyway concerned see you doctor.
HTH's
Lauren