You can also say 'I'm always doing something', but this has a different meaning. It means that I do something very often, more often than I think is normal or reasonable.
Można też powiedzieć: "Ja zawsze robię coś", ale to ma inne znaczenie. Oznacza to, że robię coś bardzo często, częściej niż myślę, że to normalne lub uzasadnione.
Jim is very untidy. He is always leaving his things all over the place.