Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your situation, and wanted to help.
Any retching, gagging, lip licking, drooling, or vomiting?
Are his gums nice and pink (not white/pale)? Moist or sticky?
If you press on his belly, does he have any tensing, tenderness, discomfort, or pain? Any soreness when you press between the back legs?
When did he last pass urine? Does he strain like he needs to go?
Could he have eaten anything he should not have (ie bones, toys, plants, chemicals, human meds, etc)?