Is it possible to fracture or break your foot without bruising or swelling?

Yes: The best way to know if you have a fracture is by having an xray.

Yes : Stress fractures do not always present with eccymosis or bruising.

Yes.: Oftentimes whether you have swelling or bruising does not correlate with whether the foot is fractured or not. You need an x-ray.

Yes... possible.: With small stress fractures you may not se any significant swelling or bruising.