Will smokeless tobacco affect my breathing?

Good Question: I am not aware of any formal studies looking at this. I would say unlikely, and it is even possible that for some nicotine might improve breathing...but surely not tobacco! The brain at your age is still developing and so the sooner you stop nicotine I think the better. Irreversible changes in the brain can occur from nicotine use, and they are more likely, the younger one is when using.