I'm drying up

So we are just down to nursing at night. I really hope to make it to 15 months. However, the last few nights after P has finished the 2nd side, he signs "more". So I relatch him and he sucks for a bit and then pulls off to sign "more" again. I feel awful for my lil' guy 'cause I don't have more. His ped said he'll eventually realize this and stop asking--it breaks my heart. I don't have a powerful letdown anymore either. Not sure if it's b/c I weaned the other feeds or b/c I'm pregnant.