What causes burning sensation in lower abdomen with nausea?

Hello,

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Well to be very honest I am not convinced with the diagnosis of IBS (irritatable bowel syndrome). IBS does cause a significant pain which is obvious in nature and show characteristic spasm like pain, not the burning you you described. Pain of IBS however, do occur over lower part of the abdomen. The burning nature of the pain suggest may be ongoing urinary tract infection, or a nerve pain within the wall of abdomen not necessarily within the bowel itself. This may be the reason pain is not responding to colofac which is an effective medication to control pain of IBS in among every patient.

I suggest you test urine detail report and ultrasound abdomen with kidney ureter and bladder to exclude if there is underling kidney or ureter stone or infections involving these organs. Take plenty of water making sure you have adequate amount of urine daily. You can continue with Omeprazole if you think this helps in this condition, otherwise you can stop these medications for now. First confirm then I can suggest you some treatment. Meanwhile for burning you can take capsule Pregablin 75 mg (anticonvulsant) at night. It causes increased sleep that why suggested to take at night. This will help nerve and muscle pain.