I'm so sorry about what you went through with your mum, and about how you've been feeling. It' s very good you've got a supportive partner and some help though.
The most important thing at work, really is just to keep yourself safe and well , and do what ever you actually need to do work wise. If people ask 'stress related type thing' , would cover a lot of things. Maybe you could even say to any management, that you have to talk to about absence, that you're choosing not to go into detail with colleagues at the moment, so you'd like anything you've told them to be confidential.
if someone is a bit pushy and you don't want to disuss it , it's ok to nicely say, 'thanks for asking and don't think me rude, but I don't really want to talk about it' or 'don't ask, I'd still be talking at 6 o'clock tonight'
When I was younger , I used to be a bit shy and I remember reading some advice about talking to people, and it said-something like, 'it's ok to just let it be quiet, and not feel you have to be the one to fill the silence'. I remember finding it really helpful sometimes , saying to myself , in a room with a few people, actually thinking, 'it's ok for it to be silent, don't feel you have to be the one to speak' . It might be helpful to think that , if someone is asking or dropping hints, to give a quick or vague answer, then if it goes quiet just let it.
The thing is , it's very helpful to talk about things that are upsetting or difficult or sad, but it needs to be on your terms , in response to what you can manage , with people you trust or choose , in a space and time you feel comfortable with, so you don't have to tell anyone something, if you don't feel like it.
I hope it goes ok and I hope you're ok , 