I got out my clarinet and began to practice some scales, but i soon noticed that my clarinet was playing an octave higher without me pressing the octave key! Does anyone know what could be the problem?

well, it could just be a reed problem with whatever reed you were using....it could also be the way your mouth is shaped on the inside that makes the reed play up an octave....or your clarinet could be broken lol

Check the pad in the register key for leaks, it might not be properly seated.