7 month old jack russell shih ztu cross lethargic and not eating?

i have a 7 month old jack russel shih ztu cross who is normally just like a typical puppy very hyper really fussy with people and constantly running about playing with his toys.For the past 4 days he has been off his food.He's eaten literally 3 mouthfuls of food in the past 4 days as i have been observing him constantly.he was drinking fine up until today were he has hardly drunk at all.He's bowel movements are normal but hasnt ped much obviously with not eating.NO DIARREOHEA he has been sick 3 times 2 of which were today the other was 2 days ago.The last time he vomited it was a pinky/red colour.he is very lethargic just wants to snuggle up and sleep.I have tried pressing his tummy/bowel area and he doesnt wince or seem to be in any discomfort..He's the first dog i have had am i been over paranoid or could there be something..obviously for him to be out of character must be something right? advice please thankyou