How could i tell if my broken collarbone (fractured clavicle) is healing?

Pain level and xrays: The pain should be decreasing over the course of days/weeks, but that actually does not necessarily mean that the bone itself is healing. The only sure way to tell is repeat x-rays.

Clavicle fracture: The fracture becomes less painful to the touch. Xrays are typically done to confirm healing.

X-ray: Followup xrays will show it is healing. Also reduction in pain is a good clinical sign it is healing as well.