GI doc dismissed me as a “healthy young woman”

I have never felt so humiliated, dismissed, unheard, and patronized. After telling my new GI specialist that I have been suffering chronic, worsening constipation, bloating, abdominal pain, and gas for over two years, and after explaining the gamut of lifestyle changes and OTCs that I’ve tried (to no avail, of course), he proceeded to tell me that he was not concerned and saw no need for testing. He “prescribed” me milk of magnesium (which I told him I have already tried) and said that as a “healthy young woman,” I do not have a serious problem. My symptoms have absolutely tanked my quality of life and wasted so much of my day, making it difficult to function. What do I do now?

Edit: thank you all so much for the support <3 despite feeling discouraged, i will definitely try to seek help with someone new!