I need a doctor or pharamacists' help?

I got some Pen Vk (penicillin) last year for a strep throat problem. I'm quite certain that I got it again...I've had it so many times I am almost positive. I dont have the time to go to the doctors this week or the next. i still have my prescription from the last time. It expired 02/22/08 so about a month and a half ago. is it safe to use it? i know its probably not as potent, but is it toxic?