My Yorkie/chihuaha Mix Has A Bloated, Hard Stomach, And Keeps Shaking! Hes Still Eating And Drinking, And Having Bowel Movements. Can You Help Me?

My yorkie/chihuaha mix ate some gum 3-4 days ago. His stomach is very hard and bloated. Hes been shaking a lot, and seems weak. Hes still eating and drinking water. His stool has been loose and greenish brown, and seems to me getting firmer each time. He is unable to jump, or even go upstairs now! I took him to tufts, they checked his gluclose levels, and they were fine. After going to the bathroom, he seems very weak and panting, and very uncomfortable. Its obvious hes in pain. Help!