Take a gravity reading. If the yeast wasn't super old, you're probably fine. I have a bucket with a bad seal that never bubbles the airlock. Plus, airlock bubbles don't mean much in terms of fermentation.
I'd clean and sanitize the airlock and pop it back in. Other than that, leave it be (after you take a reading). I bet you'll find that fermentation is happening.
Finally, being your fifth brew, I'm guessing your temps are OK, but what temp are you fermenting at?