Every contraceptive method has it's risks of failing. Some alot better than others. And using more than one is even better yet. Even when your ovulating and not using protection scientifically it's still hard to get pregnant.
If you have protected sex while ovulating and there is no problems with the control measures that you used then there s no reason to worry. You can get pregnant if the birth controls were not used properly or the condom that you used busted. The most important advice I can give is to avoid having sex during your periods as its very risky since the birth controls are not always safe.