Waking up as soon as laid down

A

I nurse my 7mo to sleep and recently he has started waking up as soon as I Iay him down in his crib. He's always been a rough sleeper. Wakes every 2-3 hours and it takes 15-20 minutes of nursing to get him to go back to sleep each time, so I really can't handle this new development of waking as soon as I lay him down. Any advice?

HELP!!!