Sounds like it might be a targeting issue. Have you run a Search Terms Report?
There is a good chance that your targeting isn’t precise enough. The STR will give an idea of exactly which search terms triggered your ads. They might be too general, or too broad, or just plain irrelevant. Check that report and let us know what you find!
If you have ads triggered by irrelevant or informational search terms (low commercial intent) then you will see results like what you reported.