Dk, in your position, I would be keeping a close eye on nappies, but otherwise carrying on as normal. Yes, it's uncommon to be pregnant with a BF baby so young, but it's certainly not unheard of, and I'm sure your body will know that it needs to sustain your older one, too. I still think DS gets plenty of fluid from me, as he doesn't drink much else and his nappies are soaked. There's no saying what your supply will do! I think mine has been up and down, but who knows, really?