My laptop wont charge when I plug it in?

Hi. Now, my laptop is a gateway (I know, horrible), and the batteries they supply usually die out after a year. So, this happend, but something odd is happening. Usually, the battery just loses battery really fast, and i have to charge it often. But for some reason, overnight, it wont charge at all. I checked the little pin inside and it's fine, and the charger doesn't wiggle when i try to make it. This is so weird, one night, it's charging just fine, the next, not at all. What could this be? Do i need to buy a new battery, a new charger, or a whole new computer? The pin is fine, and it's not wiggly. What could this be? Thank you.