Is it possible to feel your hernia one day when breathing in deeply and then it go away the next?

Yes, it is possible to feel your hernia one day and then not the next, this is called a reducible hernia, and is a good thing. Since a hernia is just a pouch of your intestine pushing through an area of your abdominal wall, many people can push their hernia back through the defect in the abdominal wall and into their abdominal cavity. It is when you can no longer "reduce" your hernia where problems arise. A hernia that cannot be pushed back into the abdominal cavity or is "unreducible" is called an incarcerated hernia and can pose more problems mainly because as intestinal contents flow through the intestine they can become "stuck" as they too pass through the area of intestine protruding through the abdominal wall. If you become unable to move your bowels or are vomiting for what seems like no reason, it may be a sign that your hernia is causing intestinal contents to back up in your system and you should see a doctor for an evaluation. Additionally, an incarcerated hernia can turn into a "strangulated" hernia because while the intestines are stuck in this defect in your abdominal wall, the blood flow to this portion of intestine becomes blocked. This causes the area of intestine to become necrotic or "die" and lead to serious problems, surgery would be your only option. Signs of this would be intense pain at your hernia site as well as vomiting. So I would suspect that on days where you cannot feel your hernia it is because that portion of intestine has worked its way back into your abdominal cavity, this is not to say that you are healed, and in fact the next time you cough or strain and the pressure inside your body increases the hernia will likely bulge out again (the only way to fix a hernia for good is surgery). A reducible hernia isn't a huge deal, but over time your chances for it to develop into either an incarcerated or strangulated hernia increase, so you have to weigh the risks and benefits on deciding if surgery would be a good idea for you or not.