What was the cause of Hamlet's to be or not to be soliloquy? Why was he obsessing over living or dying?

what cirstances brought him to that point? Apparently his "dilemma" has to do with living or dying, and "damned if you do damned if you dont" predicament" but isnt the cause of his malaise his uncertainly as to whether he really saw his father's ghost or if he was imagining it? Isnt that factor the main cause of his problems ?