I used to think dodgy meat or fish was the most likely to cause you problems but they say salads are one of the worst things to order when eating out.

Different people have different tolerances to problems with food. For some people it goes in, then straight out again with a "you must be joking" farting noise and others seem to let the dodgy food fester inside them and cause them problems.

Start making notes of where you eat/drink and what , and when you have a ... erm ... problem and that will help narrow down what the problem is.