The people who use your designs have faces. They are not anonymous, faceless eggs with little lab coats, or stethoscopes, or something that "shows" what they do.
And faces have expressions that you can draw. There is a world of difference between a sketch of a person that looks like a cue ball, and a sketch of a person that has an expression. You just need to practice.
Wong-Baker FACES Foundation
Start with the Wong-Baker pain scale. These are really simple, useful expressions that are easily recognized.
Poorly Draw Lines 1.
Or, if that's a little to healthcare-centric, then start here.
