Black stools can indicate bleeding in the GI tract, seek medical attention immediately if it has been going on a week already.(EEK!)
It could be a bleeding ulcer of some kind if you have been taking NSAIDs or Tramadol for pain relief -especially in combination with alcoholic beverages.
The lack of appetite, fatigue, stomach cramps, and headache could all be due to blood-loss. There is definately something going on in your body that needs to be checked out by a doctor ASAP. Please do not wait, it could be fatal if you are bleeding internally.