Why do I always have to do everybody's work ?

One of the best ways not to do everybody's work is to set clear boundaries with all the people you communicate with. One of the ways to do this is for example when you say "no" to stick to that no and also be consistent with boundaries you have set for others. And of course, these boundaries need to differ from the setting (e.g. family or workplace), meaning you won't set the same boundaries for people you work with and with your family. With setting boundaries, it will be helpful to set them from the beginning, the more time passes it will be harder but not impossible.