Pull the crate

You get up and pull the crate.

The ropes around your body tighten to take the strain. The weight is distributed enough that the pressure isn't agonising anywhere, but they do wrench the shoulders painfully and squeeze around the breasts, forcing them to stand out.

Perhaps the most worrying are the ropes between your legs, which press and rub on your clit with every step. It's obvious that you're not going to be able to do this in one go without cumming, probably more than once.