Can you have cushings without a tumor on pituitary and without taking corticosteroids?

Yes, one can: develop an adrenal tumor that secretes cortisone.

Yes it is possible: Cushing's disease is cushing's symptoms specifically because of a tumor of the pituitary gland. Cushing's syndrome is these same symptoms that result from any other cause. Other causes include chronic corticosteroid use, tumors of the adrenal gland or cancerous tumors from elsewhere in the body. In all cases the problem is excess cortisol levels in the blood.