Is it possible to have the sorceress curse you to never get erect without having to lose the encounter? It seems like I'm in a state where I can only access the scene where you sleep with her in you.

If you pass the Anal Addict check (3) you will receive the next portion and continue your adventure.
If you fail the check you will receive a game over and remain.

You must have a lower score than the check to pass.