Bathroom Ceiling paint keeps peeling? Very pitted

We have a problem with paint peeling in our bath room. Because of the peeling we painted it just one year ago. 4 months ago it was badly peeling again. 80% of the ceiling was pitted and bubbled up. The one wall by the shower head had bubbled up and a few minor paint peels on the wall by the window. My main concern is the ceiling. I would say 50% of the spots peeled all the way to the bare plaster. Some of the peels had water inside. So we scraped it thoroughly, patched the divots, used a latex primer, and then painted 2 coats of mold resistant latex paint. Now after 4 months it is starting to bubble up again. The house is only 30 years old. I only have that problem in the bath room, so I assume it is a moisture problem. Would using oil based primer have a more lasting effect? I notices when I applied the latex primer, it would not paint on very thick, as if it was not adhering properly. I don't know why, because I sanded everything really good. My question, is there a way to fix this problem without having to install a fan? I would be happy it the painted lasted at least 1-2 years (there is a chance we will be selling the house) without bubbling up.