Amanda my heart goes out to you! 3 years ago we had to let go of our almost 15 year old Shelti Nikki. We knew he had cancer but due to his advanced age, the vet recommended no surgery. We waited until he strated to have seizures. One night he didn't get any better and by the next am was unable to get up without help. I held him in my arms, went and got our son from school to say goodbye and took him in to the vet and held him until he was gone. Your babies eyes will tell you when it's time...I promise.
My thoughts are with you at this very difficult time.