Parenting with Crohn's: How to explain my disease to my child?

Having Crohn's disease is hard enough but having Crohn's disease as a mother is downright heartbreaking.  My seven year old son calls me his best friend.  He's always with me and it's been that way since he was born.  I can't work because of the severity of my disease, so he's become extremely attached to me, which I love.  The down side is that he worries about me constantly.  He worries that I am never going to be ok or that I will die.  No seven year old should have to worry about their mom.  It's my job to worry about him! He's an absolute sweetheart and he loves taking care of me.  These past two years have been the worst years I've had with this disease.  The pain has gotten so much more intense and I wasn't able to hide it from my son.  He has seen me scream, cry and squeal in pain.  I found out at my last hospital visit that I need surgery. I am having my anus, rectum and two and a half feet of intestines removed.  This will of course leave me with a permanent ostomy bag.  The surgery is scheduled for December 1st and because of Covid, I won't be able to see my son the entire time I'm in the hospital recovering.  This will be very tough on him.  Once I come home I will still be recovering for atleast a month so my mom is going to watch him during that time.  I am struggling with how to tell my son that I'm going to be away from him for a while.  Has anyone been through this? Even if you haven't been through this, do you have any suggestions for me? Thanks for hearing me out, I love this community.