Being in a setting that you describe as dark, and horrible, suggests that you feel you are involved in, or surrounded by a bad, or dismal, situation within your waking life.

Dark/Darkness - symbolizes ignoring of truth or fact, the subconscious, and the unknown. Darkness also hides ones surroundings, and so darkness in a dream could indicate that you feel you are being kept 'in the dark' about something and need to find, or face, the truth.

Light -  light is a very positive symbol. It represents enlightenment, lifting of shadow, the acquisition of understanding and knowledge, and a positive force. You may give the light spiritual or physical meaning. For some, the light may represent a higher force or power, God's presence, or rays of His love and peace. Others may find this dream reassuring as it may represent a well lit journey through life, or simply a solution to a current problem. Light always refers to consciousness.

Cave - Being in a deep, or dark, cave suggests you feel overwhelmed by a current situation or present problems.
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Has a close friend moved away recently, or are you moving away from your friend?
Has something happened to your friend recently and you are worried for him?
Are you in the midst of a difficult situation that is leaving you feeling alone, in the dark or abandoned?

I hope I could give you some insight. Best wishes!

just noticed the second part of the answer   thanks for the  full answer 

no none of my mates have moved away, can not think of anything that could be causing it really.

ehh no not  that i can think of