What Causes Recurring Episodes Of Sharp Pain In The Abdomen And Mid Back?

I have had 2 episodes of the following: sharp pain in my upper stomach, right under my breastbone and then extreme pain in my mid back (same section as upper stomach, but around on back). Also, I felt like I was going to faint and became extremely hot and my blood pressure dropped a little. The first time around, I went to the ER and they performed a CT scan and everything came out normal. They said it was due to constipation and possibly a muscle spasm. The second time, I let the symptoms pass and took my previously prescribed muscle relaxant and Ibuprofen 600. I felt a little different the second time, I felt more pain in my stomach and it continued as if I had gasses trapped. I took Pepcid AC and it definitely helped. Any suggestions on a diagnosis?