Mofmm, congratulations on your BFP, hope you start to feel better soon!! I know EXACTLY what you mean because I'm going through the same thing as you though not as serious as i wasnt hospitalised. Doctor said mine is only moderate OHSS around 5 days after ET and same as you, my tummy is bloated, in pain, can't lie on side, can't eat, nausea, diarhea, etc.
It been a week for me now and I'm slowly beginning to feel better. I tell myself, "moment by moment, day by day, I will get through this". Getting a BFP will prolong the symptons but it is all worth it!
Take care and hope you feel better soon! Congrats again!!
So many good news today!!