How concerned should I be about this and does anyone know why it’s happened? Pic attached

[Fascixx]

This has happened in the corner of the kitchen. House isn’t a flat roof but the kitchen part is. It’s been there a while but in last 48 hours it’s got rapidly bigger. Single parent and zero support so very worried. Any advice v v welcome

edited to add that I’ve noticed it in corners of my bedroom too but just a small bit thats never got any worse

Try to avoid that corner too, until it's fixed, and don't sit under it! We bought a house and had only been living in it a month when the whole corner of the kitchen ceiling collapsed! Was an ongoing leak from the shower above and because there were then tiles on the ceiling, hadn't realised. Terrified me at the time because my son who was a baby had his high chair there most mealtimes.

Also don't try to just paint over those patches as the damp stain will come through. You need special paint to cover damp marks (after the issue has been fixed).