umm there is a disease that your problem kind of sounds like.... its called IBS (irritable bowl syndrome) do some research and the best thing for you to eat is wheats and fiber
might be ibs/ibd if its been going on for a month now. ever had long term diarrhoea before?
oh and for the record, there is irritable bowel syndrome as well as inflammatory bowel disease. if you often have blood in your stools its probably ibd. either way, you should go see a dr.
that happened to me, i went to a doctor and he said that i was actually really constipated so whatever i ate had nowhere to go or something it just went right through me. kinda nasty, i know
lactose intolerant? it's possible, avoid dairy for awhile and see if you get better. if you do buy some lactaid pills and you're good. if not go to the doctor, it's a symptom of a ton of stuff, good and bad.