What an absolute bl*dy arse!!! You need to have a bl*dy serious conversation about his priorities! If you can afford it, then get the Nanny in every day until you are on the mend.
I had severe SPD, which was absolute agony, was on crutches, had the onset of a neurological condition which meant my legs were constantly going from under me and I had a 3-year-old autistic DS and a 1-year-old baby. My DH took over and never left me alone with our DC. Your poor little boy, he is going to be utterly overwhelmed, I am horrified that your DH would be so utterly bl**dy selfish!
Could you contact your local Shop Mobility and see if you can hire a self-propelling wheelchair? My legs were going under me so much that it was safer to swap to a wheelchair and use a connecta/ soft structured carrier/ sling to safely move around the house with my baby.
Do you have a sensory area/ sensory tent where your little boy can retreat to with a weighted blanket and sensory toys? If you do, I would put him in there as soon as he gets home. I hope that for your little boy's sake he hasn't had a massive meltdown, although it would serve your DH right if he did!
Do heat and cold help with the pain? I found hot water bottles alternated with ice packs helped a little with the pain. I am so sorry OP, I know how awful it is to be in your situation. Thankfully I had good, kind and empathic people around me when I was in your situation. I am so sorry that you have been treated so cruelly on here, you would have been better posting on the relationships board. There are too many invective and vitriolic wolves hiding in sheep's clothing on aibu!