Had pizza for lunch, massive stomache diarhea 7 hours later and nausea.this was last year and have not felt normal since.possible celiac bc of antibodies.why do i have clear stringy mucus in stool? still mucus been on gf diet for 6 months so why?

Without a proper screening for antibodies backed up if positive by tissue biopsy it is hard to blame this on celiac. You may have had simple food poisoning or food intolerance. A true gluten free diet is exceedingly hard/requiring label reading for any ingested material & prevue of all restaurant or other food consumed in public. Time to review this with your doc.