Sounds like a gallbladder or other biliary tree problem to me, particularly with the feeling of getting full quickly. Time to head to the doctor and have some tests done. Don't put it off because if it does turn out to be your gallbladder, this is only the beginning of a whole lot of misery.
Since you have asthma, the pain could be pleural (lungs) but you would be wheezing and having tightness in your chest. In any event, I think you should go to your GP as soon as you can and tell them what you have written here. A month is too long; you should be checked out. Good luck and God bless.