My jack is 1 yr old and 2 days ago after eating he trew up, he still eats purina one puppy, and now he throws up after he eats ,usually he always have his tail strait up but now I know that he does not feel good because his tail is down and he doesn't want to play and he is very energetic normally.. What can I do?

Sounds like he's going to have to go to the vet for this one.

How long has it been going on?

Can he still go to the toilet or is he struggling?

Did he eat anything he shouldn't have?

Definitely time for an evaluation by the vet... there's just too many possibilities to even make a guess.