iPhone 4S always thinks it's in the docking station

In the past few weeks, I've noticed my iPhone hasn't been playing audio through the phone speaker. If I plug headphones in, it works. When I'm in an audio or video app that supports airplay and I click on the airplay selection button, it list the Apple TV's available to send the video to but also shows "Dock Connector" and has a check mark next to it. (I'm holding it in my hand of course - no docking station).

I do jog with my iPhone in a sports arm band designed to protect it from sweat but I wonder if sweat has gotten into the dock connected port and shorted something? I wonder if it's possible to diagnose and/or clean it? I've tried a q-tip with alcohol on it but no joy.

Anybody have ideas on how to definitively diagnose and / or clean and fix? Thanks so much in advance for any advice or help!