Suggest Remedy For Pain Under The Rib Cage

I have experienced pain underneath my left ribcage for over two months now. It does not hurt when breathing only when sneezing or moving in a particular way. I haven t been in an accident or done any exercise that I believe may have caused it. I recently had tonsillitis and was prescribed some antibiotics I noticed that this pain disappeared for about two weeks but has now come back again. What could it be? I am a 25 year old female and reasonably fit and healthy.