Digestive problems..?

I went to the doctir cause i was having frquent dirrhea..they think i may have lactose intollerancy..but i dont know..sometime i get dirrhea even when i dont seem to eat dairy, im checking labels carefully and just started probiotics..i work as a groundskeeper and ride a lawnmower all day long over some very bumpy fields, could that be acting/causing it similar to runner's dirrhea? I am having to take anti-dirrhea pills usually once everyother day..or maybe its irratabke bowel sydrom or that thing where u cant eat gluton..i dunno my doctor never ran any tests or anything..?