What Causes Severe Abdominal And Back Pain?

had an episode of painful abdominal pain the other day. It was so bad I was doubled over holding my stomach. I thought it may have been trapped gas. It's been two days later and my back now hurts on both sides and stomach hurts when I cough. I purchased the AZO test strips to make sure it wasnt a bladder infection because I had urges to urinate but was unable to. The test strips are negative and I hurt worse at night time!!! I also have the Mirena Birth Control which I have had for almost 2 years now!! WHAT COULD THIS BE?!?!