Hello Friend, Good that you are seeking a help here. As your doctor confirmed that your physical health is normal, then it's the emotional disturbance like anxiety or stress which is the reason behind this issue . As body and mind are interlinked, such emotional imbalance can dysfunction and influence certain physical functions or organ.
Be positive. There are solutions available through certain lifestyle routines, dietary changes, excersise, self therapies along with counseling support.
Next Steps
Reach me online through personal chat from Practo app or call me directly to discuss in detail about your problem and recommendation of suitable solution that you can follow practically . Be positive. You will be alright soon.