I'd also say to check your E-Brake, if you use it at all...sometimes, they won't release all the way, and need to be readjusted; luckily, the easy way to adjust your rear brakes is to simply back up about 10-15 times, and then try your brakes to see where they are...usually that will solve the problem.
And, as always, if the problem persists, have it checked out by a reputable shop in your area.