Was it recently painted? How long have you owned the house?

It looks like tobacco and nicotine bleeding, but it could be surfactants leaching from bottom layers.

Leaching

I have lived in the house for 6 years and dont smoke. It had not been painted since i have lived in the house. I dont know when or if the previous owners did.

Also, i just noticed the "bleeding" when i was looking close at the stains. It could have been there for years. You can really see it unless up close to the ceiling. It may be "leaching".

Kinda looks like water staining. Not really serious. Try covering with Kilz Stain blocker---you can buy a spray can. Tape newspaper on the wall, and spray the Kilz.. Should be close to ceiling white color.

I'm also wondering if it isn't rust. I've seen water vapor (steam), slowly migrate through paint to the drywall fasteners, and when they rust, they stain.

Looks like mould. Why not try some bleach and check your fan to make sure it's working well. Good luck!

There is no fan in my bathroom.

Perhaps bleach the mould then, when taking showers, leave the window and door open a bit.

Is the popcorn ceiling painted, or just raw texture? They are very absorbent, and it looks like water damage to me. I'd remove the popcorn and make sure the drywall beneath isn't damaged. It could be something leaking from above, or simply the popcorn absorbing the moisture from showers.

The attic is above the ceiling, but it is much to narrow for me to fit in. The stains are wet to the touch. When i came home yesterday, i notice another one forming a few inches away. Maybe it is the hvac ducks? they run directly over that area.....

if they are wet to the touch, there's no moisture/steam in the room from tthe shower, and you have new spots forming it sounds like you may have a leak int he attic space above. You need to investigate further. If you can't visually see the area from the attic space above (how about with mirrors or a camera with a light and a zoom lens) then you should open a hole in the ceiling to see what's going on up there before you bother painting anything.

When the moisture from the attic (or the floor above) runs on the framing and seeps through the drywall - it will produce that brown stain.

You either have a leak in the roof (rain lately?), or a very slow leaking pipe.

I'd bet on a roof leak.

It was raining very heavily the night before the stain began. But another stain has appeared two days after the rain has stopped.

Ugh, this is frustrating.

Roof is leaking. Outside, looking at the roof, is there anything above where you have the leak - A vent? Near the chimney? Water can 'travel'

yes, i believe there is a "vent stack" very close by for the bathroom plumbling.

Inspect / change out the flashing on the vent stack. After that the only way to prove there is not a leak is a visual test going into the attic and having a helper run a hose outside on the roof. If you cant visualize it from the attic you would have to cut out the area of ceiling drywall.

Usually you can see where it has dripped off the framing onto the insulation, if you can get up there. Sometimes it will leak higher up on the roof and run down till it drips off, so the leak may be higher up.

I had a similar thing once and it turned out to be one of the molded plastic passive vents along the roof peak. Installers had bashed it with a hammer I guess and made a tiny crack on one corner so water could seep in when it rained. Sometimes the cause can be hard to find.

Could be a rubber boot over a pipe (vent stack???) on the roof needing to be replaced. I had spots in a couple of places in different rooms. had the handyman climb up, and one boot was cracked, another was almost dry rotted away. Had him go ahead and replace all 4 of them since they were like 12 years old..