child custody

me and my sons mom are unmarried.she now lives with a new guy and has no interest in sseing our son it seems like.my son lives with me and goes to school next to my house.the only time she calls is when its time for a check which i give her every week.now i find out her new guy is on herion and that she has started to do it herself.i'm afraid if i go to court she'll win custody because i live in mass and there very much for the girl.any advice would help

how long has this living arrangement been going on? im not from mass. but the longer its been this way, the better it looks for you. and if you have any proof of drug use, the judge wont allow her to take the child.