My son turned 21, lives at home, is full time student do I still pay support

My son turned 21, lives at home, is full time student. Do I still pay support

Depends on your court ordered support payments. What does it say?

You will pay according to the exact written terms of the child support agreement, You need to get it out, read it, and perhaps consult your attorney

As noted, this is spelled out in your support agreement. Absent any specifics in the agreement, then local law will apply. Since you did not give us your general location we have way of knowing what local laws apply.