How much time did you give the paint to cure before showering? What part of the wall is bubbling? The lower or upper half? Who's paint did you use?
All paints need time to cure before they can be subjected to moisture. This could be 1-2 weeks depending on the paint. It is very important to aggressively ventilate your bathroom during showering to lessen the damage this moisture can do to the paint.
To fix the problem you need to remove the bubbles, try to lightly sand the paint edges to help hide the damage. Now spot prime the repaired areas and repaint. Follow the above ventilation recommendations to help prevent this from occurring again.