"Você sempre deixa tudo nas minhas costas"
One possibility would be "Are you aware that you keep pushing your work onto me
To other situation, you could straightforward say "because of your slacking off I end up doing your work/end up stuck with extra work that is not meant to be done by me.
Of course, there are cases and cases... This answer covers just a couple of them, and I meant to the cases in which the coworker do that in a regular basis (and somehow this isn´t fair or you are not much happy with that.)