First question is: Why didn't you make a starter??? When making a starter you should add 1 day per month past expiration date to make sure your yeast is viable.
I've used yeast that's been expired over a year without any problems. As long as it was stored properly I wouldn't worry about it. You'll just have a longer lag time.
To reduce "lag time" (defined as: the time between pitching your yeast and activity in the airlock, so to speak) in the future make the starter several days prior to brewing then you know your yeast is good. You are now in the lag time phase...all you can do is wait...(if you made a starter you'd be making berr now...