Charger won't connect to the battery?

I have had my macbook for over two years now, and it has never had problems before. However, it started acting up a few days ago. First, it just randomly turned off and wouldn't turn back on. I tried plugging it in, holding down the power button, holding down various key combinations; nothing worked. I took it to the Apple store and they ran a system check and everything was fine. So I took it home, but now 9/10 times when I go to open it, it has turned off. No matter how much batter power it thinks it has, it seems to turn off. The first time it happened, I plugged it in and it came to life. However, the charger stayed green. It randomly turned orange a while later after I had unplugged it a few times and it decided to work. Today, it has done the same thing, but it's not turning orange. The battery icon has a small x through it and it says there are no batteries available. I don't want to fry the battery by having to plug it in every time to use it. I know has a decent, functional battery, I just don't know what's missing. I held option and clicked the battery icon, and it said the battery condition is normal. Help:(