( MOTHER CAN'T SEE CHILD ) HELP HELP!!!!!!

请教老猫，怎样收集证据，my ex not live with my son, my son live with grandmother's home, she can't speak English well and drive car. she is very older.she can't help child home work..

I only have other weekend visitation, very hard to 收集证据,

Last year, I went to court, tell judge, but judge doesn't care about whom live with my son. (My son always lived with grandmother home. my son school at same town. my ex lived at other town... I was show school address to judge. judge say I don't show strong 证据.

Please give legal advice.

Thx