Welcome here to the Forum. I can see it is a pretty difficult problem, on the one hand it is a job, and it is somethng your parents wish for you, on the other it is a hard thing to do, feeling used and suspecting it is harming your mental health.
There is one very encouraging thing you do say - that you are interested in working with children. To have an idea of what you want in life long term is something not everyone has, so an aim is good. If not now then at least later on.
You mentioned you have anxiety and depression, may I ask if you have seen a doctor and are under treatment? The reason I ask is that I simply did not improve until I has proper medical support, it makes a huge difference. While your parents may not take you illness seriously it does not mean things have to stop there.
Would you like to say what it is about this job that is bad?
I guess many things are balancing acts in life. I'd never suggest anyone devote their whole career on a path they did not like just because their parents wanted it, however in the short term would remaining where you are have advantages? I know you mentioned a certificate, plus whenever applying for any position being able to say you have completed something is an advantage. What do you thing your parents will do if you just left, would that make them understand?
Against that of course the effect this is having on you. A bad job can be very corrosive.
Do you think it is at all possible to partition your life, so work does not intrude out of hours? Many people try to do this, having other more enjoyable activities to keep them occupied and take their minds off the unpleasant things in life
Alternatively do you think it practical to seek out a position now in childcare? If you changed over perhaps your parents might see that in a positive light.
I'd like it if you came back and talked more about this