Can someone tell me how long will my teeth hurt from my retainer?

A few days: A new retainer may cause some pressures where your teeth will eventually settle in. This may take a few days. If this is a severe pain or long standing pain, you must return to your dentist for adjustment.

A day (or two): Your orthodontist checks your retainer when he\she first places it in your mouth to make sure everything fits the way it is supposed to. Usually it just takes a day (or two at most) to feel comfortable. If something is bothering you after that, call your orthodontist.