ESA medical assessment

Hi,

I wonder if anyone can help with a medical assessment query please? I have had 18 operations on both my legs since 2011, I have had 5 full knee replacements and several keyhole repairs etc. The latest one was only 4 weeks ago and I am still under intense physio and crutches, the DWP were notified that I needed extra surgery in December 2016 which was my last assessment. I was placed in the WRAG group and had the usual work interview which I was told that as I was taking a Masters degree at the OU that would count as work related and they left it at that. I had an assessment in July 2016 so my question is why are they sending me for so many assessments all of a sudden?
As well as the ortho problems I have bladder problems caused by the catheters which ended up enlarging my prostate gland. I had to have a bladder neck incision op which created yet another problem which is highly embarrassing as I cannot control my bladder. I suffer from depression as a result of these health problems and all of this info was sent to the DWP.
Its all very frustrating.
Many thanks in advance for any advice or info you can help with.
Cob