You have done nothing wrong!
I have often seen colleagues share personal issues like bereavement or illness/needing surgery and mention that they need to take time off because of it. It is a completely normal and human thing to do.
I must say as someone who also works in the charity sector I have been shocked many times at how the sector treats its employees and how colleagues interact: bullying, undermining, complete lack of support for people who are unwell/disabled, back-stabbing...
It is an absolute shame that a sector that always shouts about how caring and compassionate it is can in reality be very different behind the scene.
I have a long term health condition and I was really ill last year (life-threatening) and needed some sick leave for almost two months. No support whatsoever from my manager and I was asked to ignore my GP's recommendations on my first day back at work. Occupational Health thankfully reminded them of their responsibilities and told them to put in place reasonable adjustments. Colleagues also showed little support or compassion.
Don't quit over this but now you know that none of your colleagues have your back...
Seat down with your line manager and discuss the fact that you need some time off/reduce your responsibilities and agree on a plan with them.
'@SlebBB
All the SMT charity workers i’ve known have been cold and ruthless, I don’t understand your expectations. Being employed a charity doesn’t mean you’ll be soft and sympathetic.'
Really? You don't understand the expectation that people show basic human decency when a colleague is having a tough time?
Also charities rely on people supporting them through donations, grants and so on and to do that they make a big song and dance about their values and ethics and how they are on the scene to support vulnerable and disadvantage people to get their funding.
Charities expect the frontline staff they employ to be caring and compassionate people. This should also apply to its senior management or they are conning the public into financing an organisation that in fact as the same values as the worst of corporate/private companies...