I am so sorry you had such a horrible time when you were young, lighthouse, that's very sad to read. I guess there was a lot less understanding in general about these things.
My understanding is that emet can start one of two ways - either a traumatic experience as a child (which often involves shame/humiliation - throwing up in school for example) OR the opposite, when you haven't been sick for so long you kind of build it up out of all proportion. With DD we think it's the latter, she hasn't been sick since she was a toddler.
I know what I've described (with the pretending to be sick etc) must sound absolutely unthinkable to you but honestly, the process is gradual and it works. I remember reading the whole book when I first got it and DD was in a terrible place and just feeling completely helpless, because is seemed like an absolute impossibility that that she would ever be able to even think about some of the exposures.
But just like the OP describes we started small and you just do it again and again and again until you can tolerate it. Then you find something just a tiny bit harder and you repeat it. Interestingly for DD the process actually got easier and easier as she gained confidence in it - I remember her sobbing and sobbing at watching a video of someone just telling a funny story about being sick. But by the time we got to pretending to throw up, she was just mildly anxious at the prospect and it really wasn't a big deal.
Don't get me wrong, she still has emet and perhaps always will, but she is in control now, not the phobia, if that makes sense.
I know I sound like a bit of a nutter but please do buy the book and give it a go.