Problems with my iPhone 3GS Charging

I've had my iPhone 3GS for about a few months, and it was working fine until now.

One day the famous 'Charging is not supported with the accessory' sign came up, which i kind of fixed by blowing into the iPhone and getting rid of the dust that was stuck in there.

But then, i was worried when i woke up this morning and turned on my iPhone, which was at 2% but when i went to bed i charged it 100%

is there something wrong with the iPhone? or the Charger?

Its iOS 5

Thanks

Was anything running in the background? I don't think the message you got had anything to do with it draining so quickly overnight. I get that message regularly, but my phone only loses about 6% on standby overnight.