Lizzy, sometimes people have a way of expressing concern that makes you feel claustrophobic and criticised.
I love love, love my mum, but she does this too, and whilst it's mostly fine, when it's about something that matters to me, sometimes it just hits a nerve. For example, when I bought a 2nd-hand car off a relative recently and had to drive it from the North home to the Southwest, she kept on and ON about how it was dangerous to drive so far on my own, weather was bad, couldn't I just leave it a couple of months and do it in the spring, etc, etc. She was really expressing concern and even offered to look after the car up North for me!
But things like that, especially about something as big as a job you love, and especially when you are depressed, can start feeling like nagging instead of caring. Your parents sound like they care for you, so I'd suggest saying next time you are over,
'Look, I know it probably seems crazy to you, but you know I've felt really bad recently, and this job helps me feel sane, gives me my own space. Can you support whilst I keep working there for now? I will leave one day, but not read to yet.'