puppy fever

so currently I've been trying to get my parents to rescue another dog. I feel like if I had a dog that loved me as much as our current dog loves everyone else but me and my brother my depression would ease up a little but I'm terrified to tell my parents that because they'll either say I'm just saying it to get what I want or that if my depressions that bad I should go see a therapist (which I have asked them to set up an appointment for me since I'm only 17). I've been looking at Bulldogs who need rescued so my dad's reasoning that they'll be too rough for my nana is invalid due to the fact they all have medical issues and love to just lay around and they are very good with other dogs and will work with our current dog who is a hyperactive brat. a bulldog would actually be better for my nana than our dog is. (nana lives with us) any suggestions on how I convince them to rescue a dog for me? this is Brutus, the dog I'm trying to rescue.