Last time I went to France I was really badly constipated too - and I couldn't figure out why. Is it the food?
Anyway French people are a pretty constipated lot (don't tell them that!). Unlike say the Germans they are not really into the Bowels. And their fibre intake is appalling.
OK so what to do? If I were in your position first thing I'd do is a salt water flush. 1 litre warm water + 2 teaspoons (unrefined) Sea Salt .