Can someone please tell me how to tell if my heel is cracked or fractured, etc.?

Be seen. If you had sufficient mechanism to have fractured it and it is painful to bear weight, it could certainly be fractured. Consider being seen, an exam and appropriate studies will likely reveal the issue.
Heel pain. Most of the heel pain I see is due to plantar fasciitis which is inflammation of the fibers attached to the heel. Typically worsened on first weight bearing. However stress fracture can occur and regular x-ray or even MRI if symptoms are refractory would be wise. Talk to your pcp.
Need to look see. Micro cortical calcaneal fractures can occur routinely with severe cases of plantar fascia strain. Unless the heel is showing an obvious angular deformity and there is a traumatic or medically compromising reason for the fracture, there is just no way of being sure without some type of imaging.