Why won't my iphone 3 charge?

I brought an iPhone3 or 3GS off my friend who has never used it, in a week of having it the brightness like went weird and turned down, and I tried to adjust it but it wouldn't work the more I tired this the darker my screen went so I left it alone and when I came back to it the screen was so dark it hurt to try looking at it but any who dad took it to a repairer and they fixed it that was like 3-4months ago.

But now it won't charge I've tried it on all 3 chargers in the house I've put it on different outlets I've tired to put it in the laptop but it won't recognise it, I've also used the toothbrush cleaning trick and it won't charge
What else can I do?

Try shutting it down by holding the power and home button at the same time. Then try to hook it up to the computer while it restarts. It still sounds bleak though.