I've cleaned the lint from the sockets but my iPhone and iPad still won't charge?!?

Hi guys, for around 3 months I've had trouble charging my iPhone and iPad. I have searched the internet for solutions and many people have said that to solve this you should clean the lint from your product and the usb connector, I've done this and there was hardly any lint and when I plugged it into the mains it didn't even charge. So I've recently bought two new connectors to see if they'll work, and they did for about 2 months, but now they're just like my older connector/usb. I'm really confused because this is so annoying and it's really difficult to charge any of my products as I often have to move the phone and connector into certain positions for it to even work! Please help me, because I have no idea whether its the products themselves (iPhone 4s and iPad 2) or the connectors or the mains plug itself?

Thanks guys!