"We had such a great relationship," says Karen, a high school senior who asked that her real name not be used. "I loved him so much." 

And so she had sex with him. Not because she physically wanted to have sex, but because she believed, on some level, that she needed to give sex in order for her boyfriend to keep loving her back.

Unfortunately, Karen has plenty of company. 

Many teenage girls believe that sex earns them love, according to Sharon Thompson, a journalist and author who has interviewed more than 400 teenage girls about their sexual and romantic experiences. 

"The way teen girls think about sex is tied to their ideas about love," says Thompson. "Some think, for example, that sex proves love." 

Sex, Etc.'s informal survey of girls who have had sex confirms this idea. The girls interviewed said that, looking back, they know they had sex hoping that their boyfriends would fall in love--forever. 

But it didn't work out that way. 

"He fell out of love with me," says Karen. "And now I'm left here with nothing but memories. It's been over five months, and I still don't know how to get on with my life." 

Protection for the Heart?

"A condom offers a very high percentage of protection against disease and pregnancy," adds Jane, a sophomore whose relationship ended after her boyfriend left for college. "It can make you feel safe. But, there is no way to protect your heart. You can't put a piece of rubber over that. 

"Last year, if someone would have told me about all the emotional hurt and responsibilities that come with sex, I probably wouldn't have listened and would have done it anyway," adds Jane. 

"But I wish someone would have told me. Maybe then I would have stopped and thought about it, or at least I would have been better prepared to deal with things," she says. "Not in the fantasy world of true love, but in the realistic world where love and pain often go together." 

Ask Tough Questions

Sharon Thompson offers some advice. "It is important for teens to recognize that ideas about love, sex and reproduction have a history--and that they can be questioned.'' In other words, says Thompson, girls need to ask themselves some tough questions before deciding to have sex: Am I having sex because I want sex or because I think it will make my boyfriend love me more? Am I having sex to please myself or someone else? What do I want--now and after? 

Take the time to figure out how you feel and then stand up for your feelings, says Thompson. If his love is real, he'll love you for who you are--whether or not you decide that sex is what you want.