Hi there, I am really sorry to hear about this uncontrollable pain you have during sex. I do get that too but since my hysterectomy it is not nearly so bad but during doggy style, yes I still get the knee dropping pain during sex. We do the missionary style a lot of times just so that we can have sex because most other positions are painful. I will usually take a ibuprofen a half hour before sex or at some point (anti-inflammatory and for pain) and after sex use a heating pad on the abdomen or take a hot bath or shower. It is probably your cervix that is causing this pain and if he is 9 INCHES ? he's huge and he is definitely hitting something in there, he should be taking it easy with you right now, DO NOT let him penetrate you fully until you are healed - just like a bruised muscle when you work out your sex organs will need a break too to heal properly. Doesn't mean you need to stop just don't penetrate all the way and do mostly missionary right now - most other positions you get fuller/deeper penetration which is when he is more likely to 'hit' one of your lady organs inside.
Hope this helps