I can't convince my girlfriends son not to call me daddy.

I took the father's role when he was 1, but now after a grueling 2 year long battle to adopt him we've lost and he gets to see him every weekend. We're now suppose to make it clear to him that I'm not daddy but he just laughs and says I'm being silly. Am I at a point where I put him in time out if he calls me what he's always called me? What am I suppose to do? via /r/Parenting https://ift.tt/2U3HSJK