I somewhat disagree with the first sentence of your post: new borns are never boring! At least from the standpoint of their parents. Even if the baby does nothing, it is just the most amazing thing ever. This being said, I stopped at 2 kids… but for other reasons. Concerning mind games, this starts early and somehow… never ends. Except that with older children, it is a fairer game and we can all play (niark niark niark). In particular with my 10 years old boy… we have a lot of fun on plauying each other!

On the topic, I had never noticed any habit coughs with my kids, so that I am afraid I have no experience to share. I can imagine the stress that should be yours (at least at the beginning when you were not used to it). Good luck with this and I wish you good luck in unravelling the mystery!