Hi ya Peaches
I've suffered from very painfull periods since the age of eleven. I've had
all the usual treatments (mefanamic acid, contraceptive pill, being patronized). I don't have fibroids, endometriosis, polyps, cysts or PID, so my experience is going to be different to yours, but I hope my advice will be useful.
I've just started using a TENS machine (after passing out in the middle of the job center because of overdosing and mixing painkillers) and I've used it for the last few periods. I'm using one that was designed for labour pains. I use it with painkillers so that I can stick to the recommended dose most of the time!
It does work, but it's like smudging out the pain with a prickling sensation which is much easier to handle. It's like getting rid of the noise of a dripping tap by putting on some music.
The sensation is like the static electricity off a TV screen, almost itchy. The type that I am using has conductive pads with some kind of goo on them and they are reusable as long as I don't get fluff on them. When I go to work I duct tape them in place because if you are moving around a lot they tend to slip off.
It's best to turn up the current gradually over several minutes. I find that if I do this I can build up tolerance to the sensation and get the full effect. Switching it to full mode straight away can be a shocking experience!
I've got a unit with pulse and continuous current. I prefer to use continuous as the pulse mode can be quite ticklish.
My unit is battery operated and I find that one battery can last a whole morning or afternoon. The unit itself is so small that it can clip to my belt. I find that I have to use the unit for about a quarter of an hour to feel the full benefit.
During my lighter days I find that I can use TENS alone, but for the worst part of my period I have to use painkillers as well.
Hope the above is useful. Hugs and kisses and lots of good wishes - Cybermintzzz