What Causes Pain, Swelling And Numbness After C Section?

Hi I had a c section 10 weeks ago and am still in pain and have alot of swelling. I had an ultrasound today and they tell me I have some fluid in my uterus maybe a sign on an infection but I am already on anitbiotcs called Augmentin. They are wanting to do more tests ie a MRI scan. My scar site above is very hard and swollen. I also have pains below my sternum is this muscle damage?? Can you shed some light on to why I am still feeling bad. Still have pulling feeling and cold numbness on pubic bone.