I can't sit still but tested negatively for add. what could it be?

I wonder ?: What "test" proved you did not have adhd.The use of those initials (add) make me curious as to who gave you the test.I'd recommend a test administered by a dr. Who diagnoses and treats adhd.But;that said, not sitting still is not enough to diagnose adhd.

Other influences: You are most likely to perform well when you are well rested, well nourished, free from illness and in a comfortable setting. If you can improve on the factors that you can control and still have a problem, it is likely a different condition and or anxiety related. Further workup along those lines may give you a way to manage the issue.