My 5 year old cairn terrier pees all the time?

My wife and I recently rescued a dog from a no kill shelter. The first month he was with us he was great except for peeing when we would put a leash on him or he got to excited. We continued working with him and thought it would go away. Over the last month it has gotten much worse. We cannot put his leash on him without him peeing. He has also gotten to where he pees on the couches as well. We tried putting him in his crate and he got very upset and peed in his crate for 7 straight days. We are getting very frustrated with him, but we love him very much. We have called a vet and they told us it was submissive peeing. Also recently he pees when he gets upset, he recently peed on both of our shoes when we corrected him. We also tried correcting him but it made it worse. WE NEED SERIOUS HELP, WHAT DO WE DO? If we can't fix this, we may have to get rid of him.