I was hoping to get some responses back to my request for more information, but I don't want you to go without any answers.
Many yorkies have liver shunts. It is a problem in the breed and a liver shunt can lead to seizures. Additionally, very small breeds can develop hypoglycemia (low blood sugar) if the don't eat several times a day. Low blood sugar can also lead to seizure activity as well. I know your dog is currently not having seizures so it is possible they were the result of low blood sugar and not a liver issue. Let me give you some information on liver shunts and hypoglycemia as well as seizures in general and then I will address the current issue.
Hypoglycemia is low blood sugar and can cause seizure activity especially in small breeds. Feeding your dog smaller meals more frequently can help. If you suspect your dog is having low blood sugar you can put a drop of pancake syrup on your dog's tongue which should raise the level. As a dog matures they are better able to regulate their sugar supply and hypoglycemia is often no longer a problem unless they stop eating for an extended period of time.
A liver shunt is usually a genetic condition. It is a condition where instead of the blood going through the liver and being cleansed, part of the blood is diverted around the liver resulting in a toxic buildup in the blood which can lead to circling. You can read about these here: http://www.malteseonly.com/shunt2.html
You can read more about seizures here:
The behavior you are seeing here sounds like he may be having some back pain or an issue with a disc in the back. When you pick up a dog under the front legs like you do children, it puts a lot of pressure on the discs in the dog's back as the weight of their rear is pulling down on the discs. This can cause pain for the dog. They can start to associate you picking them up with the pain. Cries can be related to pain as can depression. The proper way to pick up a dog is to place one hand on the chest between the front legss and scoop the back legs and rear into the other hand and lift straight up so the spin stays pretty horizontal. This will reduce any pain when picking him up.
If there is some disc injury, then your boy might avoid stair and jumping as well. Your vet might want to do some imaging and give an anti inflammatory medication to help with any pain and give the area time to heal. Read more on disc issues here:
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.