pain in chest

I am a 40 year old female in general good health- 5'7" 168 lbs. Since I was about 15 I began experiencing chest pain on my left side. I have had EKG and electocardio grams-No problem found. I find that stress or severe lack of sleep sometimes causes my pain. Some times the chest walls feels as if an elephant stepped on me and can be sore for days. Then at times out of nowhere I will experience sharp pain in my chest and back-my left hand and arm feel strange and sort of numb down my pinky and ring finger-I feel that I must hold my breath because breathing feels like I may explode or feel worse pain. When the pain is happening I usually keep quiet and it goes away in 2 or 3 minutes which seem like an eternity. I got really scared and had to talk myself out of a panic attack on Sat. because this happended to me in the grocery store. I was not stressed and I had had plenty of sleep, during the "episode" I just stood at the icecream freezer and tried to keep focused and appear normal-I did not want the attention. The pain was more severe and stretched from my left breast through my back and down my left arm. I thought I was having a heart attack. My breathing was normal and I did not have a rapid pulse. After I was tired and drained. Later that evening I had severe gas pain and flatulence all night and the next day. My chest was sore and I was tired. I rested for the rest of the weekend and was fine on Monday. I am lactose intollerant and sometimes I have low blood sugar-however my AC1 blood test came back normal. I have to be careful with coffee because it makes me jittery and feel low. Diabetes runs on my maternal side- Most often the chest pains and migrain headaches come one week on either side of my period. Could this be a hormonal or metabolic thing?