20 Year Old Female. Fairly Healthy. I've Been Having Bad

20 year old female. Fairly healthy. I've been having bad chest pain for nearly a month. Middle area gets tight squeezing sensations and sometimes stabbing pains. Left side gets stabbing pains especially around the heart, that seem to shoot around the whole left side sometimes to my back. Sometimes I get a pressure pushing sensation around my heart on the left side. I feel like my heart twitches or skips a beat sometimes during the pains and sensations. Catscan, EKG, and X-rays were done the doctor said it is not the heart. Pain relievers only help for half an hour.