Hi Lilybella. No, I don't think OHSS is a certainty, and I think the riskiest period has now passed.

DW had 26 eggs collected on our first IVF stim cycle and had oestrogen levels of 18-19,000 and apart from being quite bloated, had no apparent issues with OHSS, although her ovaries did remain swollen for a bit.

Drinking plenty of water is very helpful, but we were told no more than 3 litres a day, so be mindful of also not drinking too much and diluting your system of essential minerals and salts.

I think at this stage you'll be fine. Good luck with this cycle.