This habit bites! (Body: Q&A).

I can't stop biting my nails. I've tried bad-tasting polish and rewards. I've even spent my allowance on manicures. Nothing works! I want my nails to look nice for my spring dance.

You have the solution right at your fingertips! Really wanting to break this bad habit is the first step to stopping. You already know nail-biting hurts and looks awful, but did you know it can cause skin infections and make you catch more colds because you expose yourself to germs? Try the following tips from real readers who've licked the habit for good. Kellie, 14, bought herself a ring, and she says wearing it keeps her from gnawing her nails. Rosemary, 12, talked to her mom about her anxiety and went to a doctor to find out how to manage it. And Alison, 13, carries a nail file and clippers in her bag at all times and uses them instead of her teeth whenever she's tempted.

When I'm falling asleep, my body twitches and, sometimes, it wakes me up. My friend says the same thing happens to her. Why?

These pre-snooze body movements are called hypnotic jerks. Just as you go to sleep, your heartbeat slows, your temperature falls, and your muscles relax. All this happens before your brain has completely powered down, explains pediatric sleep expert Dr. David Gozal, University of Louisville. As your mind prepares for R&R, it fires off extra brain waves that cause your limbs to move a little. Researchers aren't exactly sure why this happens, but they say nearly every person (with or without realizing it) experiences this before drifting to sleep.

One of my nipples points in; the other one points out Why? Am I abnormal?

Breasts come in all shapes and sizes- even on the same person. One might be a little bigger than the other or, as in your case, one nipple can be an innie while the other is an outie. Yes, like belly buttons. All these differences are perfectly healthy and normal. In fact, up to 10 percent of all women have inverted nipples, explains gynecologist Dr. Adelaide Nardone. Breast innies happen when the connective tissues that run from the center of your breasts to the milk ducts, located just underneath your nipples, are slightly short. So the nipple pokes slightly inward. Since you're still growing, there's a chance your nipple will poke out one day. But if it never does, who cares? There's no health risk in having an inverted nipple.

When I was changing my pad, I noticed a bunch of little white bumps "down there." They're freaking me out! What are they?

Relax. They're completely harmless. You probably noticed the little glands at the opening of your vagina. On that area where the skin is smooth, there is no hair. So to protect that delicate tissue, the glands, called papilla, secrete a tiny amount of oil that keeps your private parts healthy, according to Dr. Nardone. Another kind of bump that might pop up around your panty line is a plain old pimple. Either way, as long as you're not sexually active, you have nothing to worry about. Your body will go through a lot of changes during puberty, which is totally normal.

Stumper of your own? E-mail it to [e-mail], or write to Body Q&A, Girls' Life, 4517 Harford Road, Baltimore, MD 21214.

RELATED ARTICLE: Fact or Fiction?

Tight, hip-hugging jeans are hazardous to your health.

FACT. Yep. Skin-tight low-risers are "the" look. Britney loves 'em; your mom hates 'em. Sorry, but your mom wins this one. A canadian doctor warns that the jeans can squeeze a nerve under the hip bone, causing tingling or burning sensations in your thighs, called paresthesia. The good doc recently, treated three young women with this condition who'd been wearing low-rise pants regularly for six months. After the women traded their hip-huggers for looser-fitting clothes, their symptoms disappeared. Paresthesia is not life-threatening but, if ignored, can cause permanent numbness.