My 14 yrd old son is seeing a counselor. i am the custodial parent. he wont talk to me.what do i do?

his mom (non custodial parent) took him twice. his mom texted me the other night that we need to sit down and talk. me, her and the 14 yrd old child. we agreed to go to his counselor. my son told me that he promises me that he will not sit in the room with me, his mom and the counselor. his mom told me that he would be willing to talk if it was just me, his mom, and him...but for some reason he does not want me to talk with the counselor too? what would make a child not want his parents (espcially with his dad, who i have had custody of for 13 of his 14 years) to meet with the counselor? my son will not even come by the house (i live 1/2 mile from his mom) and at one point he told me when i asked where he was he said (i dont know (idk))