Can herbs cause dampness?

The best person to ask is the acupuncturist that you are currently seeing as they are most familiar with your case and have had the benefit of physical diagnosis. But to answer your question generally, yes, improperly prescribed Chinese herbal medicine can cause any number of problems. More specifically, using moving herbs/formulas when there is deficiency that is not being accounted for can cause weakness and loose stools - among other problems.

You don’t really mention how often you are seeing your current practitioner or what they herbs are that they gave you, so I wouldn’t really be able to do anything other than speculate a time frame. Generally, I would imagine within 3-7 visits (so 1-3 months) your issues should be resolved.

Generally speaking you should also avoid dairy and soy products as well as raw. Try not to eat meats or other high protein foods with a lot of carbs as that slows down digestion as well. Also try not to eat dessert on any kind of regular basis - a big dose of sugar after meals is also terrible for digestion.