There are no 'disorders' that I know of that will cause that constellation of symptoms-- which is the case so often with this forum. It is clear that many people have symptoms that cause a great deal of discomfort, fear, distraction, and distress... but that don't have clear medical reasons. Patients become frustrated with their docs, and the docs frustrated that their patients don't do the right thing and get better! There a couple points worth making.... one common fear that I hear is that the person has a serious illness like cancer. A frequent frustration is that the doc doesn't want to do enough tests to satisfy the fears of the patient. Then there is a desire for symptom relief, let alone the fear of significant illness. Many times I am frustrated as well, as I would like to come up with something helpful for people that come here
In your case, Leanne, you are describing what sound like two different things. The sharp pain sounds the least likely to be 'serious' because it has been there for awhile and hasn't progressed and presented itself. Sharp pain in the chest related to breathing is often 'pleuritic' pain, meaning that it relates to the sensitive lining of the lungs or chest wall. But I can't think of something that would cause pleuritic chest pain for a period of years, without getting worse and presenting itself-- say as a pneumothorax (collapsed lung), pneumonia, or pulmonary infarct (sort of like a 'stroke' of the lung). So instead you probably have some nerve fibers that are more sensitive than they should be, and that occasionally start firing off pain signals that are worsened when the lung is inflated and the fibers are stretched.
The other pain is something to keep an eye on if you can feel a painful mass. The most common source for the pain would be as you put it-- an area of inflammation and pain from a pulled muscle or maybe a large lipoma, or fatty tumor (that is benign). Some masses need to be checked out fairly quickly-- breast masses in women, for example. other masses can be observed- like ones that are in the subcutaneous tissue, as yours appears to be. Things that are worth checking out are masses that are very hard, or that are 'fixed' to adjacent tissues. Lumps and bumps that move around freely and don't seem attached to the tissue around them are more likely to be harmless. These are, of course, generalities.
As for symptom control I recommend using anti-inflammatory medication like aleve or ibuprofen. Using opiate narcotics is usually a mistake, as their tolerance makes them more dangerous than they are helpful.