Microphone on ipad2

The microphone on my ipad is terrible (I have tried various ways of cleaning it). People can barely hear me when I use Facetime. I bought a cheap plug-in mic (to be plugged into the headphone socket) and people can now hear me - but I can't hear them! I guess this is because my ipad thinks I've plugged in headphones and shuts off the speakers. How can I get sound when the mic is plugged in? Alternatively - do I need to buy a USB microphone (they all seem very expensive)? Any other solutions to the problem? Thanks