According to Dr. Karen Rosewater, it takes approximately one month after starting the pill for it to become effective in preventing pregnancy.

It is a misconception, though, that condoms are the most effective method of birth control. Aside from abstinence and sterilization, the pill and other hormonal methods are the most effective contraceptives we have at this point.

However, the pill does not protect from sexually transmitted diseases and infections, so condoms may be a good back-up plan.

You said your boyfriend had been tested--probably for HIV--but there are other sexually transmitted infections that cannot yet be tested for in men, such as HPV caused by the human papillomavirus, which has been shown to increase a woman's odds of getting cervical cancer.

In the face of the unknown, it's probably best to be covered on both fronts--pregnancy and STDs. Therefore, you should consider using a condom along with the pill.

Take care.