What Could Be Causing Sudden Nausea, Dizziness, Vomiting, And Diarrhea Whil Climbing Stairs Or Walking On Steep Roads?

Hi Sir when I climbed stairs , suddenly I felt nausea , dizziness followed by vomiting and diarrhea, some times it happen when walk on steep road. i experienced this incidence almost three times in last two months, what could be the reason to which doctor shall i consult. please advice