I am not completely sure but I think I recall reading that in a woman who has no problems become pregnant that it is okay to use a commercial lubricant. However for a woman who is having problems concieving the lubricant makes it harder for sperm to swim to the egg. The best lubricant is the natural fertile cervical mucous that a woman has for a few days before she ovulates.
If you are consistantly dry, there are things you can do to help. Do you where tampons. Because of the absorbancy of tampons, they have a tendency to take away your natural moisture also. There are also chemicals in the tampons are will also dry you out and may be causing harm to your dh's sperm. Tampons are bleached in the factories to make them completely white. The bleaching agent is then not rinsed out because it will ruin the tampon. There has also been cases of asbestos found in tampons. (asbestos makes you bleed more - and then you use more tampons)
I quit using tampons about 6 months ago, and about the 2nd month my normal moisture returned. <IMG SRC="http://www.healthboards.com/ubb/smile.gif"> (also my flow because much lighter!!!!) If you feel you must use tampons, try organic tampons, sold at natural, or herbal stores. or only use them during the heavist flow. Hope this helps. Sheila