what should i have done??

the best players know when to fold AK, remember..."everybody" knows that a small pair can bet the AK. Depends more on you and your opponetns stack size, your position and how your opponent has been playing. If he/she is tight, I'd fold in a heart beat. If he's known to be a lose player, well...

Sometimes you have to fold and commend your opponent for a great bet.