My partner has borderline personality disorder which is supposed to share a lot of traits of bp, I am not informed enough to say whether it is true

So any way that's the back story now my point.....

I can always tell when he is gonna have a bad episode because he will initiate dominant/submissive sex, normally taking the submissive roll himself. I may walk upstairs and find him 'tied' to the bed and in a blindfold or another of his favourite ways to initiate it is by texting me from the other room asking if " mistress wants anything "

I don't believe it is part of his mental illness but more a case of when his mood is turning it influences what he wants sexually. In the same way that in certain times during my monthly cycle I just want wham bam thank you Mame I not interested in being tender or foreplay.

As for your childhood influencing your sexual preference I think that's also fairly standard; I find sexual images of women a turn on and especially girl on girl pornography but have no desire to be intimate with a woman on any level. I believe it to be a learn association that naked woman equal sexual arousal. After all the modern world is full of advertising, magazine covers and TV saying as much.