My DS did this too. We went cold turkey no dummy when he was about 8 months old as he would wake anywhere from 5-10 times a night for it to be put back in his little mouth. It was hard work but worth it as I hate seeing children 3 and 4 with dummy's in their mouths. But he has never been a great night time sleeper, at 18 months old he has only just started sleeping through the night in the last 3 weeks or so. Good luck!