It's certainly scary to know someone who has had breast cancer. I can understand your anxiety.
Here is a link on how to do a breast exam on yourself: http://ww5.komen.org/BreastCancer/BreastSelfAwareness.html?ecid=vanityurl:28/ You will also find information on that site about breast cancer prevention and detection.
Most care providers recommend a mammogram every year after the age of 40. Up until then, self examination of your breasts once a month, and examination of your breasts by a midwife or doctor once a year is what is recommended. Unless you have a history of breast cancer in your family (your mother had breast cancer, for example) or if you have certain risk factors yourself, you can probably follow the usual protocols for mammography. It's a good idea to talk to your midwife or doctor about your fears so that you can find out what is a good plan for you.
There are some people who don't believe mammography is the best tool to use to visualize the breasts. Some people think ultrasound is better.
Keeping yourself healthy and low risk would be a very good thing to do. Having a good diet, getting exercise, not smoking ... these kinds of things will help keep you low risk for cancers of any type. It's never too late to change habits. When you do have a baby, breastfeeding has been shown to reduce the risk of certain cancers in the mother, including breast cancer.
Please feel free to post again!