The most moving testimony at a public hearing yesterday on teen-age pregnancy came from five young mothers, who openly told a packed auditorium at Ballou High School in Southeast Washington about their experiences -- and their mistakes.

"I had to learn the hard way," said Sherita Dreher, 18, the mother of a 2-year-old child and a senior at Ballou. "My parent never taught me to use contraceptives."

But it was Mayor Marion Barry who drew the liveliest response from the 800 assembled teen-agers at the hearing, sponsored by his "Blue Ribbon Panel" on teen-age pregnancy. The mayor promised to "tell it like it is," and did.

"Sometimes, sex is good to you, but not good for you, especially if you get pregnant in the process, isn't that right? I'm just telling it like it is," said Barry, drawing applause and laughter.

Barry appointed the panel last May to investigate the widespread "crisis" of pregnancies among District teen-agers. Panel chairwoman Joyce Ladner said 1,792 teen-agers in Washington had babies last year.

Ladner said Washington has one of the highest rates of births to teen-aged mothers in the nation, and declared that the problem has reached "chronic" levels in the black community and is tied to "a lack of parental guidance and relaxed social mores."

Ladner, a professor of social work at Howard University, said last year's teen-aged mothers accounted for 18.8 percent of all births in the city.

In most cases, the births forced the teens to drop out of school, Ladner said. She added that Ward 8, which includes Ballou and is one of the poorest sections of the city, had 23.6 percent of all births to teen-age mothers last year. That figure is second only to the 25.2 percent rate in neighboring Ward 7, she said.

According to national statistics, 560,000 teen-age girls give birth each year and babies born to teen-agers frequently are born prematurely and have a higher risk of serious health problems.

Ladner said similar hearings will be held in each of the city's eight wards before the school year ends in June and she expects to hear testimony from a broad spectrum of teen-agers, including youths in primary grades, Hispanic youths, and students from middle-income families.

"Girls, keep on saying 'no,' " Barry said. "To those young men who don't want to hear no, tell them to 'get the heck out of here.' "

Ladner said, "teen-age pregnancy is one of the most chronic problems of our times. It's a crisis in the black community. It begs our attention and begs our intervention."

The panel includes 91 educators, health experts, social scientists and city administrators, she said. Eight members were present for the hearing, which was held "to share concerns and ask for suggestions" from students, she said.

While there are numerous health and social services for teen-agers after they get pregnant, more needs to be done to educate parents and youths about ways to prevent pregnancies, she said. An anti-pregnancy slogan contest will be launched in city schools soon as a way to increase awareness about the ills of sexual intercourse, she said. Also, the panel will urge ministers to preach against premarital sex, she said.

"Most girls get pregnant so they can get a welfare check," said Joye Jackson, 16, a junior at Ballou and mother of two daughters, one 10 months and the other 22 months old. "I get $236 a month. What's that? I can't buy baby's milk or clothes to put on my back."

She said the father of her children, a 17-year-old student at a Maryland high school, "didn't have to say he loved me to make me have sex with him. It just happened. If passion hit you, you're gonna do it."

"The first time I laid down I got pregnant," Jackson said. "The second time I used an IUD intrauterine birth control device and still got pregnant." And she added, "I do not believe in abortion."

The next hearing is scheduled for Nov. 20 at 10 a.m. at Fletcher-Johnson Educational Center, Benning Road and C Street SE, Ladner said.