[M'lord]

Predicament bondage is indeed hard to describe, hope the below makes sense.

Required kit: Chair, string, rubber bands, nipple clamps, bottle with gradual taper (such as a Perrier bottle, I would recommend an unopened plastic bottle, file off any sharp bits, as it has a base that will help hold the string) or similarly shaped object, and lube.

Optional kit: Blindfold, gag, headphones playing white noise (a bit of sensory deprivation helps add to the sensations), additional pair of clamps.

Setup: Tie the string and rubber bands togeather to form 2 lengths. Tie one end of each to your hair in the centre of the back of your head and the other to your nipple clamps. Pass under your crotch and clamp on to your nipples. The tension/stretch should be as such that with your head in a normal position the strings should be snug but not pulling, and, when pulled a bottle length away from your crotch, pulls your head right back & provides an unbearable tug to your nipples.
If you wish, you can also add similar lengths tied to your big toes and clamped to your pussy lips so that when sitting on the chair there is no pull, and an unbearable stretch when lifted up by the bottle length.

Remove the clamps and allow your nipples/lips to recover before continuing.

The Main Event: Put on the gag and headphones (If using) and lube up the thin end of the bottle. Insert the end of the bottle into your arse, bring the strings under the base of the bottle (ensuring that they can slip fore/aft but not escape from under the bottle) and position yourself over the chair so that the bottle base is resting on it. Attach the clamps to nipples &, if using, lips, slide the blindfold (if using) in place. Now, using just your fingers bring yourself to orgasm 3 times before releasing yourself (note, if you can't achieve this in the time you're happy to wear clamps for add a time limit instead).