Since you mentioned the vomiting, I think there may be more of an issue other than teething and a slowed growth spurt (which a lessened appetite would indicate). You didn't really expand on his vomiting (or his health history), so I wonder if he caught a stomach bug. It would explain his getting sick and loss of appetite. If has been regularly throwing up for a while, I would investigate other things like food allergies and reflux. I would be concerned about his fluid if there is a big decrease in wet diapers as well. All considered, I think you should contact your doctor's office and speak with the nurse practitioner that most ped's should have on call for these types of things. They know you, your child, and your child's health history and can best diagnose and/or advise you on this matter. Good luck!
As for the teething