For starters, you can't miss with an authority like the Harvard Center for Women's Mental Health. If you haven't found your answer after reading their materials, you might find another tidbit or two here -- but they are probably the world's authority on this topic at this point.
Surfing around looking information on PMS, as you may have seen, turns up a lot of sites. About 90% are trying to sell a product. The vitamin B6 site doesn't mention the nerve damage that has been associated with this treatment. The bottom line: be careful, especially if somebody's trying to sell you something. Here are some of the better sites I found (there are surely many more; you can write and tell me if you find better stuff to put in here -- thanks):