My RE says that the fluid released is an irritant. And if you have that many follies, you will feel it more intense. I have had it as bad as you say, where you feel like you are being cut in half :) It will go away. Good luck.
I had IUI on Sunday and Monday and the day after the trigger I had really bad O pIn on the right like never before!! I could barely walk too! It was my 2nd cycle on Femara and Gonal F and this time had 3 mature follies so perhaps why it was more painful? The pain lasted about 5 hours or so.
Now, I've had a couple of instances of right O type twinge very mild (I don't usually get that). However I'm also on prometrium so who knows.