I have a 18 month old jack Russell cross, he's always been a fussy eater and sometimes won't eat all day, and then give himself hunger pukes. Last night he bought up yellow bile 3 times and just wanted to sleep. He's had some water but won't eat. This morning my DH encouraged him to play with his toys and he was more than happy to do so, but as soon as he stopped, he just went back to sleep. He has since thrown up very watery white foam and is now flat out in bed. He's responsive, will bark if a noise alarms him as usual but doesn't want to eat anything. What should I do?