Firebrand, I'm 9 days ahead of you and had a total breakdown last week, so I totally hear where you're coming from.
Queenie gave you fantastic advice. As I've told my husband, I can work or I can make dinner, but I can't do both. Monday I stripped the bed and left clean sheets on it and told him to make it. (He did.) After last week, I went to my boss and told him I made a mistake in coming back full time so quickly, and we worked out a bit of an easier schedule for the next few weeks.
If I were you, I'd call the school and explain that I just had major surgery and can't navigate around the school. Would it be possible for the teachers to send you updates by email? ( You shouldn't have to walk around that school 4 weeks after hip replacement. Seriously. You don't want to have a setback.)
Call your best friend and cry to her. Like queenie, I've noticed that if I cover up the difficulty I'm having, everyone assumes I'm just fine and bounced back so quickly, and they have their own **** to deal with. If she's really your best friend, she'll listen and apologize for being out of the loop. (And if she's not, you might as well find out.)
You're amazing, Firebrand. I absolutely could not have gone for 2 20 minute walks, made dinner and baked a cake yesterday. In fact, I took the ingredients out to bake before I left for PT yesterday, and ended up putting them away because I was too tired. My husband was away yesterday so my dinner last night was black bean soup from the freezer and a glass of rose. (I highly recommend the wine.)
As for work, it's hard not to feel uncomfortable but try to let that go. You'll be back in the office soon enough--you can bake them a cake to thank them for taking over some of your responsibilities and let them know you'll take it from there. Hold your head high. From what I'm reading you're an amazing worker and your boss is lucky to have you.
I hope tomorrow is a better day for you. XO