When it comes to information about sex (and weird penis problems), we're more likely to believe a doctor than our friends. The only problem is that we're more likely to actually ask our friends -- at least they don't charge a copay to explain the difference between cold sores and canker sores, even if they mix up which one is herpes. (Or likewise confuse your bikini area sunburn for an STD.)

Fortunately, Mental Floss just made a video with Dr. Aaron Carroll, author of the charmingly titled book "Don't Put That in There!: And 69 Other Sex Myths Debunked," to explain the top 20 misconceptions people have in the bedroom. Watch, learn and correct your gullible friends.