How do I know if I am getting answers from board certified doctors?

Check the Drs. bio. Doctors all have a bio that includes board certifications on this web site. If you're talking about your real doctor in the real world, just ask -.
Great Question. I think that's one of the flaws of healthtap, but you can easily find out if a particular physician is board certified by going to www.Abms.Org, the website of the american board of medical specialties. They have a search engine that will allow you to look up a specific physician and view his certification.