I don't think its food poisoning tiggs, my husband had EXACTLY the same this week, freezing cold, couldn't get warm, very very weak, sick during the night, then the next night so hot, the bed was soaked I had to change all the bed clothes etc. Its the winter vomiting bug I think, very catching, so disinfect all surfaces well or the family will catch it. Good news is that it only lasts two days but leaves you weak. I gave him Lucozade and the first meal just plain cooked chicken and plain rice which he kept down. Hope you feel better soon.