left side sharp chest pain sometimes shoots to the right

I have had left side chest pains for the  past 4 1/2 months. These are sharp pains a hand width below my collar bone. Occassionally I have had the same pain shoot over to the right side.  While the pain in my left side moves around that general area and lasts 30 second or less at a time. The pain on the right is straight across.  I have had 2 ekg's, blood work and chest xrays.  So far my doctor has not found anything and says he doesnt think its my heart.  I am a 36 y/o female.  I dont have high blood pressure, I am overweight, but have lost 50lbs in the last year.  I feel that maybe we should be doing more tests, but the doctor thinks it will be fine, with no explanation. I have no family history of heart disease or problems.  The pain occurs "whenever", not with physical activity.  In the past year I have also been diagnosed with IBS. I cannot get a second opinion without a referral from my doctor.  What can I do to get more answers, and should I be worried?