Sorry to hear your baby is not feeling well. I would think that his wanting to share your pizza is a very good sign. Maybe he ate something like an acorn or leaf that didn't sit well with him.
But, I was just about to suggest canned pumpkin
when I saw that @Floki
had posted about it, too. I use it all the time with my three dogs, one being a chihuahua. It is great for all kinds of stomach/pooping issues. Also if I think one of my dogs ingested something bad , I grab the canned pumpkin and give them a few spoonfuls of it. The high fiber can help make the foreign item pass if it is not too big.
***Use only canned pumpkin with NO ADDED SUGAR. I find it at my local grocery store on the baking aisle for 79 cents a can.
I mix it into my dog's bowls with their regular meals. If I have to give extra portion, I generally put some chicken broth or cooked meat juice mixed in to help with the taste/smell.
If your dog isn't drinking, to avoid dehydration, you could boil some chicken with water and then give your dog the broth from that. We make chicken like this often and then I pour the broth into ice cube trays and freeze, then put the cubes in ziploc bags for later use. And the chicken we cube up into small bites for training treats and freeze as well. Convenient, cheap, and healthy! And they love it, esp when they aren't feeling so great.
I really hope your doggie feels better soon!!!
Keep us posted, ok?