Do you mean cut, or clamped. when you say clipped? If it was just clamps (some people call these clips), one could have dislodged and let the tube be open again. Take a pregnancy test and see if you are pregnant, is the obvious next step.
Woah, if your tubes were clipped then you are def not pregger, unless the baby is growing from another body organ, but def not your tubes ;) dont worry. Consult your doc and they will give you the run down.