Excessive gas belching breathlessness help!!

[Rainbowunicorn123]

I am a 21 year old female currently suffering daily with constant excessive gas to the point I can't lie down breathe properly or sleep! I have constant gas belching hundreds of times daily (every few seconds)! I have been on the Yasmin pill for 4 years recently switching to cerelle in the last 4 months. I have had all routine blood tests, a double ended scope in large and small intestine, an ultra sound and a biopsy for coeliac.. All of which came back negative apart from one of the blood tests showing extremely low alkaline phosphotase! I have also tried the FODMAP diet but nothing helps I have this constant pressure and gas regardless of what I eat or drink. I eat a healthy diet and am I healthy weight? Can birth control be causing this? Can anyone shed some light on what this might be???