Monday I have to postpone my teaching session with Christopher, so I can attend my appointment with a rheumatologist. The last time I taught in school was 10 years ago, when a particularly vicious form of arthritis struck; it took me out of the classroom after barely a couple of years.
But today my thoughts focus on a new and incredibly effective medication I've been taking for the past few weeks.
"The disease is no longer active. You're in remission," the specialist tells me. I sit back, awash with happiness.
"There's one drawback." I nod. I can accept any side-effect, as long as I'm free from this disease.
"We don't know the outcome of becoming pregnant on this medication. I advise you not to have children."
Tuesday I am helping seven-year-old Christopher to form the letters "a" and "d". He looks up. "Do you have any little boys of your own?"
I shake my head.
Wednesday Christopher is not giving up. He looks up from the "d" in the salt tray, wiping a white finger across his nose.
"Do you have any little girls?"
I shake my head.
"OK. Any big girls, then?"
Thursday Christopher has practised "a" and "d" on the magic slate and we have been building consonant-vowel-consonant words. As we pack away his reading cards, he says conversationally: "My nan couldn't have children."
Friday Christopher's mother phones to say her son's cold has come out, and could we miss today's lesson? My husband decides to take the day off.
Wandering around an end-of-season National Trust property, we get chatting to a young mum with a toddler.
"Have a good life, Amy," says my husband to the little girl, as we make our way to the exit.
It's only then that I find I am able to cry.
Imogen Carr is a home tutor in Berkshire. She writes under a pseudonym