Well, it could definitely just be a phase that he will grow out of in a month or so. But until then, I suggest letting your husband be the one co-sleeping with him, until he learns he can't nurse all night.
Or, if you can be strong and hold out, do what I did...........
When my daughter was 16 months, I just refused to let her nurse in the middle of the night. I knew it was just a comfort thing, and she didn't really need to eat. So I just wore a crew neck, long shirt to bed so she couldn't get my shirt up, and pulled her close and snuggled with her. She would fuss and cry a little, but I just held her and kept whispering, 'Mama's here'. After a few nights, she gave up and slept through.
I know, it can be so frustrating. But kudos to you for doing this for your baby.
To 3BoysUnder3: J. asked for help from breastfeeding, CO-SLEEPING mamas. Perhaps you missed that......