Implantation is the attachment of the fertilized egg, the embryo, to the uterine lining. It usually occurs about a week after fertilization and ovulation.
While you may be pregnant if you feel cramps about a week after ovulation, having cramps alone around the day of implantation doesn't always mean that you are pregnant.
The fertilized egg is very tiny, and you are unlikely to even see it with your naked eye. Because it's so small and has little impact on the uterus, implantation is usually not associated with cramps.
Of course, it's possible that your cramps were associated with implantation but still, the cramps are not a sufficient enough sign that you are pregnant. You still may have to wait for typical pregnancy symptoms or a positive pregnancy test to confirm the pregnancy.