Hi Jayne
I don't know anything about your blood levels as I wasn't measured but I got mild OHSS after ET once. The advice on drinking water is absolutely right - it's to make you pee out the hormones so you don't produce and retain fluid (which is what OHSS does). If you had it really badly you would be put on a protein drip, which for some reason cures it, so you should also eat plenty of protein (this really helped get rid of my symptoms) - meat, fish, eggs, cheese, nuts - until you go nil by mouth of course.....
Also drink a pint or two of milk or soya milk, this kills two birds with one stone - fluids and protein.
After EC keep drinking and eating protein as you can still get OHSS.
I know people talk about cranberry juice on this site, but I always thought that was for urinary infections like cystitis, not OHSS.
Try not to panic, OHSS is avoidable if you know what to do and what to look for. If you bloat up so that it becomes very uncomfortable, keep up the fluids and regularly peeing and call your clinic. If you start to rapidly put on weight (ie through fluid retention) and/or have difficulty in breathing then you must go to casualty immediately.
Hope you feel OK soon, and good luck for your EC. I'm sure it'll be fine.
Claire x