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It sounds like he is having a vaccine reaction. This can cause not only the regular signs of facial swelling, vomiting and diarrhea but can cause muscle pain, fever and lethargy. If there is an emergency vet in your area, I recommend going there. If not you can give benadryl at home but I recommend having him seen tomorrow if he is still not wanting to eat or move. Do you need help locating an emergency vet in your area? Do you have children's benadryl?
If you did, you could give 1/2 of a 25mg tablet or about 1-2 mg per pound. However, an emergency vet will be able to give him an anti-inflammatory injection as well as a benadryl injection. This should make him feel better in an hour or so.