This is a very common question that creates a lot of confusion and fear for young adults. Whenever we hear about condoms and how effective they are, everybody throws around the fact that condoms are 97 to 98 percent effective at preventing pregnancy. But what does that actually mean?
When people say this they mean that about 98% of women that use only condoms for contraception over a years time will not get pregnant, while the other 2% will. This 2% of women that end up getting pregnant does include women who get pregnant because the condom broke. They all used it properly, but for whatever reason, the condom can still break. Most of the 2% of women that get pregnant have a broken condom to blame. Other then the condom breaking, there is really no way for the semen to get into the vagina around the latex condom.
If you are extremely worried that condoms are not effective enough or are afraid of one breaking, you can always use it in combination with other forms of birth control (such as birth control pills, birth control shots, etc.) just to be safe. Lastly, if you do use a condom and it ends up breaking you can always use Plan B emergency contraception or other products like it to decrease the chance a pregnancy will occur.