Guilt in a dream usually points to something unresolved -- a wrongdoing, real or perceived, that your conscience hasn't let you set down yet. Confessing in the dream can reflect a wish to finally address it directly, while being unable to explain yourself often names how stuck the self-blame still feels.
When the Moon and lord of the ascendant shall be impedited by the lord of the 8th, the sick person hath cause to fear. - William Lilly (1602.-1681.)