Topic: Please help!

Please help! We have a website which is a year old in a very competitive adult toys market. Certain keywords are jumping around in the rankings. They can be on page 2 one day then not in the first 20 pages for a few days then back to page 2. This is happening with about 5 different keywords and we aren't doing anything unusual with link building and publishing articles (I don't think).
Does anyone have any suggestions?