Minecraft Single Player Game Problems?

When I updated Minecraft all my games disappeared! I don't know what to do. I did not make back-ups, so I'm not sure if I can get it back. When I played Minecraft it was also on a different computer and I before I played on the different pc I didn't play MC in a long time because of pc problems. Could that be why my servers are gone? Because I did not get on MC in a long time? Please help and tell me If I can possibly get my games back please.

Yes, that's the problem. You stopped playing the game, and since it wasn't use in quite some time, the save files get erased. All games tend to do that.