Does condom prevent pregnancy? my girl is not on birth control, and i am worried about that the condom maybe breaks inside here?

If it breaks....: A condom does provide good birth control if used properly and it does not break. If it does break (a problem with this method of birth control), pregnancy can result. There are other more reliable forms of birth control out there (iud, ocps, depot provera, (medroxyprogesterone) etc.). It is a matter of personal choice with regard to what risk you are willing to take.

Condoms Used Right: Condoms used right, with lube, are universally good to go for sexual intercourse. If the intercourse lasts a long time, then lube is either reapplied or a new condom is exchanged so that you do not let it break. There is also a female condom that men often prefer. The condom fits inside of the vagina, is fully protective as well and is not tight against the erect penis.

Condoms: Are not 100%, but then nothing else is either. If used properly and appropriately their effectiveness is usually estimated at 98%, but there is no way to know exactly. Some people use two condoms, others add in another contraceptive method at the same time to increase safety.

15% failure rate: The failure rate of condoms in typical use is 15%, meaning of 100 couples relying on condoms at the beginning of a year, 15 will be pregnant by the end of the year. Using condoms plus a spermicide (vaginal suppository, jelly, cream, film) lowers the risks of failure. Condoms can slip off or break. Couples who rely on condoms need to know about emergency contraception as well, given the 15% failure.