That's one of the oldest myths out there! The average penis is around 6 inches long when erect. Some are bigger, some are smaller — and shoe size has nothing to do with it. In fact, vaginas range in size more than penises. The truth is, you can't tell by looking at a guy how big his penis is, just as you can't tell by looking at a girl how big her vagina is!

When guys get sexually excited — like from kissing or making out — and they don't ejaculate, blood builds up in their testicles (a.k.a. “balls”), and they may ache and appear slightly blue because of the blood. But never let a guy convince you that if you don't do something sexual with him, you'll leave him in major pain. The pain is minor, and he can always masturbate to relieve himself later.

When guys hold their urine in for a long time — like when they're sleeping — it can cause an erection. That's why morning erections are so common; it doesn't necessarily mean a guy is turned on! But guys also have a higher testosterone level in the morning, which can make him get an erection while he's sleeping.