Dreams involving pets, especially traumatic scenarios like decapitation, can evoke strong emotions and often reflect deeper feelings or anxieties in your waking life. Here are some possible interpretations of your dream:

1. Fear of Loss: The decapitation of your dog may symbolize a fear of losing something or someone important to you. Dogs often represent loyalty and companionship, so this could relate to your relationships or feelings of security.
2. Anxiety and Stress: The graphic nature of the dream may indicate high levels of stress or anxiety in your life. It could represent feelings of helplessness or being overwhelmed by circumstances beyond your control.
3. Change or Transition: Seeing your dog in such a state might signify a significant change or transition you are facing. Decapitation can symbolize a severance or ending, suggesting that you might be dealing with the end of a phase or relationship.
4. Family Dynamics: The reaction of your family in the dream could reflect your concerns about family matters or how you perceive their responses to your own challenges. It might indicate a shared anxiety or fear within your family unit.
5. Guilt or Regret: If there have been situations where you feel you have let someone down or caused pain, this dream could be a manifestation of guilt or regret regarding those situations.

To better understand the dream, consider your current life circumstances, emotions, and any recent events that might have triggered these feelings. Journaling or discussing your feelings with someone you trust might also help you process these emotions.