Re: help please
I agree that I think 13 months is young to try and night wean. 13 months is tons of milestones, so probably he's too busy exploring during the day and is making up for his nutrition needs at night.
Can you try and nurse in a quiet and dark room? Might encourage him to take a bit more during the daytime.
Really though if you hang in there it will probably swing back the other way in a few months time.
Are you co-sleeping? Might be worth it for a while while he's going through this night nursing stage atm.