what could be causing and what to do

my 6yr old yellow lab has had all shots but is an outdoor dog. has not been eating normally for about 2 weeks but for last 5 days wont do anything but take in a drink of cold water. we cant even bribe him with his favorate snack throws up green vile once a day     i am ***@****

[Margot49]

Sorry to hear you dog isn't well.  Those symptoms could be caused by any number of things.  Any chance he ingested something?  
The first thing I would do is give his mouth a *good* inspection checking for anything caught, loose or infected teeth, irritated and/or infected gums.  If that seems to be okay, I think I would take him into the Vet, esp since this has been going on for 5 days, for a check up.  When you do go, take a fresh stool sample with you to be checked.

[Ghilly]

My first thought would be a bad tooth or teeth as well.  If it's not actually a tooth, it could be that he has something stuck down alongside a tooth in the gum.  If you do find anything stuck in his mouth anywhere, even if you are able to remove it, I would still take him to the vet to have him looked at since he might need an antibiotic to combat any infection that could be caused by whatever it is that was stuck.  Five days is a long time for a dog to go without eating, so you want to get on this quick!  Look in his mouth tonight and WHATEVER your findings are, get him to the vet tomorrow.  You don't want him to go any longer without a good meal!   Think of how hungry you would be if you had had nothing but water for five days.  You'd be hurting from hunger, so you want to resolve this, whatever it is, ASAP.

Ghilly