We're all different, but I suffer from ibs, and 2 consecutive days of salad is enough to set it off. Also, i don't know which type of lettuce you're eating, but iceberg is well known for causing problems for a lot of people with ibs. Maybe give salad a miss for a day or two, and it might be worth trying dairy and gluten free food for a while to see if that helps. Trial and error really to see what helps, and what causes problems.