What Causes Chest Pains And Inflammation?

I am a 21 year old female experiencing sharp chest pain on the left side of my chest, made worse when taking a breath and moving in different positions. I had it for about 4 years now with only around three episodes a year in which it lasts a few minutes to a few days, the pain was quite moderate but I did have one episode that it lasted a few minutes of server pain but it went away just as fast as it came about a year ago. At first I put it aside like nothing but was assured to get it seen about. When it occurred last night before I went to sleep and stayed chronic the whole night I went to the emergency room this morning in which my blood pressure, EKG and x ray came out normal even though they said they seen a little inflammation in my chest area and asked if I had phenomena, asthma, been sick in the past months and other questions I answered no to which I thought was weird because I never had any problems in this area and have not been sick in over two or three years. I am not the only one with this problem; my mother also has chest pain but in the middle of her chest mainly when she was working. She went to the emergency room several times and the test they ran also came out normal. Does anyone have a clue as to what this could be? I did some research in which I cannot find a direct cause.