i had a root canal done thursday, went back to the dentist saturday because it hurt real bad when i drank something cold, they took the filling part out and took another nerve they found out. now the numbness wore off and the tooth is throbing but no pain when i drink something cold. is the throbing normal, if so for how long??

I don't know. But you basically had the equivalent of two root canals on one tooth within a couple of days, so I could see there being throbbing or pain.

Here's what I found on a dental clinic's web site:

If a throbbing sensation occurs please keep your head elevated as much as possible and place extra pillows under your head when lying down. Avoid as much as possible any strenuous activity as well.

So maybe you should take it easy and then call your dentist on Monday just to be on the safe side. I hope this helps!