Good to know I'm not alone J! Many thanks for your response.
It's getting worse each time I shower again but I'm keen on finding ways to deal with this.
Oddly, I don't actually get this as much, if at all, with baths - possibly because baths are "open", but in a shower I am kind of "boxed in", which better allows the heat to be contained.
Every so often I have to open the shower door and take deep breaths of the cooler air on the outside, try to shower with the shower door open so that fresh, cooler air comes in (but this doesn't last long because I don't want to get the bathroom floor soaking!), or sometimes I'll just end up sitting down in the shower doing nothing like I'm going to fall asleep.
When I come out in the end though is when it seems to get at it's worst: me trying to dry myself and put my clothes back on whilst feeling like crap urghhh -_-
I haven't fainted before though that sounds nasty :( I hope we can find some nice ways to help alleviate our symptoms here!
Sending much love! x