My 18 month old american staffy has all of a sudden this afternoon started throwing up and now he won't eat or drink anything I have tried all his favourites and he normally will do anything for food but he is just sniffing it and not opening his mouth for it or he gets it in but spits it like he wants to but can't I noticed this morning he was doing some really smelly farts but other then that he seemed to be fine but we had a sleep after he threw up the first time when we woke up he was really noticeably unwell and he threw up again this was not large but flemy looking he normally is very hyper and does many tricks he is not interested in doing anything we got him to play but even then he was not his normal self and he is normally a very cuddly creature he really doesn't want much to do with me or my partner and we are struggling to get him to do anything we tell him to we have just moved in with my parents and there little dog, which has caused a bit of a flea problem which he has come out in sores and rashes we were giving a spray for the rashes and just yesturday fleaed both dogs and the house that is improving but this is the second time in 2 weeks that he has become off colour but yet this is the first time he has refused to eat or drink I don't know what could be causing it and I am really worried about him

Could it be possible he has come into contact with something toxic?

I suggest bringing the dog to the vet if he won't eat or drink.

I agree with Red, vet is in order. Could be Parvo, could be many different things. And if it is Parvo, your parents are going to want to take their dog in as well. It is a very deadly disease.
You should try and get a flea treatment from your vet. They have some really great flea and worm treatment combo's. I like Revolution. I am not a fan of sprays, flea baths or flea collars. They rarley do what they are supposed to and can be more harmful to your dog! Try bathing in Dawn dish soap if you can't get to vet for flea treatment.
Flea's and worms go hand in hand. That's why the combo treatments are the best.