Hi Bella Mum
congratulations on your pregnancy!
Unfortunately OHSS is something many of us doing IVF have to deal with. I think in most cases the worst of the symptoms clear up fairly quickly (it really just depends on how severe you get it in the first place). I think I had about 2-3 weeks of pain, then it more or less went away. I was still very bloated for months and my ovaries were still enlarged at the 20 week scan.... But once the pain went I felt ok.
I hope it clears up for you pretty quickly and you can enjoy this wonderful time

All the best,