I meet my new Mistress for the first time

‘I didn’t say that you could get hard did I?’ Sandra said as she slapped my erect cock with her hand. I was shocked by the stinging pain in my throbbing member and her savage response to my erection. I thought she would be pleased with it.
‘Make it go down, I don’t like the way it’s flapping around’.
‘I can’t’, I pleaded, ‘Once I get erect it stays hard for a long time’.
Sandra stared at me icily, ‘You really are a disobedient little slut aren’t you?’
‘Yes, Mistress’ I mumbled.
‘What did you say?’ Sandra asked.
‘I was just agreeing with you that I am a disobedient little slut’ I replied.
‘Good, at least you understand that much, there is hope then that you can be properly trained’
Sandra strode over to the other side of the room and picked up a long piece of rope and something else that I couldn’t identify.
‘Since you can’t make your fucking cock go down I am going to do something about it to stop it from moving around’, ‘put this on’ she commanded handing me four rubber rings connected together with a small leather strap. I realised that what she given me was a device that was meant to be fitted around my cock and balls. One of the rubber rings was larger than the rest and I guessed correctly that it must be slid down my cock and then I had to force my balls through it as well so that it squeezed them up tight. The other three rings were only just large enough to fit around my shaft and once they were pushed into place they began to squeeze into the flesh of my cock further inflaming my erection. Sandra took the rope and doubled it up at the middle to form an open loop, she then put the loop across my belly and fed the ends of the rope around my back and back through the loop at the front. Pulling down hard and tight, she took the loose ends down either side of my cock and between my legs. The ends were then pulled tight across my buttocks and brought around the front again and fed through the two ropes at the front. Sandra then pulled very hard on each end and I gasped at the sudden restriction it caused. ‘Did you enjoy that bitch?’ Sandra asked with an evil laugh. I knew what I had to reply, ‘Yes Mistress, it feels nice’.