paint all peeling on bathroom ceiling, please help?

Hi, Having a bit of a disaster painting the bathroom ceiling

The house was built new 4 years ago and they painted everywhere including the bathroom ceiling with Armstead contract matt white paint, there was some bit that were starting to chip a little. I had some left over paint that the guys gave me at the time we moved in to touch up bits that may mark while we are moving in etc, so there was less than a quarter in it.

So i decided I’d give the bits that are peeling / chipped a scrape and then re-paint over the part of the area that’s directly above the shower, as i was doing it lots of the ceiling was coming off onto the roller, so i completed what i wanted to do then when i went up to look at it around 6 hours later a lot of the ceiling had peeled really bad.

I have now re-scraped all that and used the last on the paint i have on putting it back on, i know it will need more coats though so i have ordered another 10L of it (can't seem to get smaller) but it isn't coming until Wednesday.

I have a feeling there might be more peeling after this use but maybe not as much (fingers crossed).

Any help with this at all and why it’s done that?

The board behind where everything as peeled seems in good condition and not wet to touch etc.

Thanks

James

When I started decorating, a complete novice, still an amateur, I learned that the plaster needs to be primed before you apply a paint, otherwise the paint will keep coming off after some time. Having to paint the bathroom ceiling myself soon I will defo use the primer as the previous people certainly neglected this important step, or maybe just relied on the paint containing the primer. The paint comes off in areas that are not exposed to the steam directly, the paint holds very well above the shower. So it apparently was a problem of a dirty plaster board (got the spot lights on the ceiling).