I transitioned more than a decade before the Equality Act existed, when trans people did not have legal recognition through the GRA, but were still allowed to use single sex facilities that best suited us.
Who gave you the permission to use the facilities of the opposite sex?
Was it in a work situation? Did the management call all women together and tell them that a man was proposing to transition, he wasn't to be discriminated against and there is a question of which loo he will use. Were they asked if they minded, with the veiled threat that no one could say they did, or was it presented as a fait accompli - he will use the women's loos and you will put up with it.
I suspect it was the latter. I would have been narked seeing you go into a woman's loo but as long as you nipped in, relieved yourself, washed your hands and nipped out, I would have let it go. This might well not have been the case for a woman who had been raped or sexually assaulted, had a melt down and also spends nights crying over the experience. Did you ever think of that? I would suspect not.
Your complaint is not with women as a class - it lies with those people who told you, you could change sex, and it lies with trans activists who being given an inch haven't taken a mile, but taken ten thousand miles and are now ranting and raving.
So please take your complaints to them.