Gone your history carefully and noted that no physical abnormality is there .
Thing to note is that your develop symptoms ;nothing help except bowel movements
I feel you are suffering from episodic panic anxiety
disorder To you may appear a strange diagnosis but beleive me psychiatic disorders present mostly in strange ways
Nothing is helping so try consulting a psychiatrist who will throughly evalute you psychologicaly and if agree will give you a combination of SSRI
Anti Deprassant drug plus anti anxiety drug which may make you feel better over period of time if you take it regularly
Recover soon and give me feed back