Gas cramps diziness on and off. Be?

After eating a lot of gas and burps. I also had fever when these symptoms started with severe acidity. Dizziness and fatigue was also there. Dizziness continued for few days. History of Constipation. Now no fever or dizziness. But little bit of stomach cramps burning sensation specially after eating. CBC done - Haemoglobin in slightly low 12.8 g/dl rest everything is normal. CPR is high 6.8 mg/dl. Also has an episode of similar symptoms 5 months back which was way more severe. Also had black stool last time. Low bp continuous, had to take IVF twice as ORS was not enough. It took around 15 days to recover. Last time in October stool occult, cbc, LFT, WIDAL, Dengue Rapid Test (Igg/Igm, DGNS 1) tests were normal. Only ESR was 55 mm/hr. USG of whole abdomen was normal. Also having back pain and dry mouth since few days. Dr. is suspecting stones. What are your thoughts, what could this possibly be? Please help