Sick Jack Russell Terrier (serious answers only plz)?

My dog will not stop vomiting (it's yellowish in color) and he has diarreah really bad. It started while I was at work today. I did notice him acting really weird last night though, laying right next me the entire night, not playing or eating. I have cooked some plain white rice and tried giving him more water. He will not touch either of them. He keeps wanting outside so when I let him out he finds a spot to 'go' (number2) and tries but nothing is coming out. His stomach does appear to be hard. I have not changed his diet nor anything else in his routine, however, he did go to the vet 2 days ago for his distemperment shot. Surely the shot isn't making him do this, it didn't make him sick the last time he got his shots. Can I give him any pain relievers, what kind? how many miligrams? Oh and he will not stop panting, does he have a temp? How can I check that? Help!?!