8 year old step son may or may not have add or adhd

My step son has been bounced back and forth between his mom and grandma they are both a little crazy. Neither one have ever really wanted him but they didn't want us to have him. They have had him on loads of meds for add or adhd whatever suits them at the time they had him on sleeping pills because they were double dosing and keeping him wired up on pills. Now when we got him last summer we took him of the meds with our doctors approval and our son did fine he was better behaved and slept better with out the meds but when he went home they put him back on the full force. The mom has custody of him for now and she had changed his meds and his diagnosis 3 or 4 times in the last six months. We have joint legal custody and the mom is suppose to talk with us concerning all meds, doctors appointments and everything. He will be back this summer and we are going to get the doctor to make weekly visits and document his behavior when on and off the drugs and see if we can compell her to keep him off of the or if not maybe we can compell the courts to hear us out. We really don't know what to do.