How can stress affect your chances of conceiving?

It is a biological thing. You are not creating an supportive environment so your body does not accept a pregnancy. In ancient times, a woman would be "stressed" if she was struggling to live due to food or environmental changes or perhaps trying to keep too many other children alive. They body's response is to delay conception as there is little chance of a baby surviving in these circumstances. Make some changes in your life - it will be well worth it. Stress effects your chances of conceiving in the sense that stress effects your period cycle and ovulation cycle.