Your little boy is adorable and very much so still a puppy... I agree with DvlshAngel985 that you should use a phrase to ask him if he needs to go to the bathroom and make sure to ask him each time before you take him out. We us "Do you want to go outside?" to mean do you need to go potty, and they get to know to whine and then when you ask the question, my two get all riled up and I know they need to go potty.
Good luck in your training! It's a lot of work, but they are well worth it all
