Why won't my ear buds won't work?

I plug my ear buds into my computer, and only the right side will work. I thought it was my ear buds, because their cheap and they break easily so i bough two new pairs and both of them do the same exact thing. But, i tried plugging them into my iPhone and playing music and both sides work perfectly on all three pairs. If i push the ear bud jack Really hard into the computer and hold it there, it's really choppy but works but as soon as i let it go it stops. I have no idea what i did to make my computer do this, it was working fine 4 days ago and then it suddenly started doing this. Any ideas how to fix this?

A jack is actually the female connector that you plug into on your computer. The solder for that jack has come loose and you no longer have a viable connection for one of the channels. You can fix this by opening the case of your computer and finding the circuit board that the jack is soldered to. Using a soldering iron you can heat the solder and remove it with a wooden toothpick and then resolder with fresh solder. Let cool and then test. Repeat if it doesn't work the first time. If you get a good solid solder and the jack doesn't wiggle at all and it still won't play on the other channel, then replace the jack itself.