The symptoms you are experiencing could be withdrawal symptoms (
headache, fears) or flashbacks that usually occur after prolonged ganja (cannbis) use. The feeling of
depression could be a result again of prolonged ganja use (amotivational
syndrome) or else it could be related to a
mood disorder (depression).
Stopping ganja use was an excellent first step. Continue to abstain and the withdrawal symptoms should disappear gradually. Because ganja persists in body tissue this could take upto 4 weeks.
If the symptoms are interfering with your work and relationships you should consult with a
psychiatrist. This would help provide immediate relief and also address the important issue as to whether you have an underlying mood or other psychiatric disorder requiring treatment.