Phyrexian unlife, losing life

[Klazam]

I know i cant pay life, but what effect does losing life have?

Case in point:

The enchantment on the board, and i cast Ad Nauseam, while my life is at 0 or less. Can i draw my deck, without me losing?

thanks.

[Malchar]

Your life total goes below zero. You can end up with your library in your hand.

[Klazam]

excellent.