Check out this article from CNN.com. It's a list of 10 'secrets' you shouldn't keep from your doctor. I was amused enough at the list that I thought I'd share it for those who don't want to read the full article.
1. Smoke, drink excessively, do illegal drugs
2. Have peeing or pooping issues
3. Take herbs
4. See a chiropractor or an alternative healer
5. Are having financial troubles
6. Want cheap medicine (i.e. generic drugs vs. brand name)
7. Feel depressed or anxious or stressed out
8. Defied the doctor's orders
9. Don't exercise and eat badly
10. Have a small problem you think is unimportant
I'm not sure why this struck me, in some ways, as funny, but it did. My primary physician is one person I really do tell everything to! After a heart attack two years ago and the realization that I'm getting older and older every day, I figure I'd better keep my doc "in the know".
First of all, I pay her to make my health a priority (for her and for me). Second, some of these things I think she'd know if I tried to lie. For example, defying her orders or not exercising and eating badly will show up in her examinations of me for the most part. If I leave her office and return six months later and have gained 20 pounds I think she'll figure out I've not been a good girl with diet and exercise. Finally, what's the point in keeping secrets? It's kinda funny but mostly sad to think that people would not tell their doctor about things because they were embarrassed or frightened of the reaction they'd get or maybe they just don't want to be told any bad news so they lie to avoid it.
Anyway, if you have a fear of being honest with your doctor, try finding one that you feel comfortable enough with to be completely open. I think you'll be glad in the long run and likely a lot healthier too.