What does it mean to have cramps off and on a week before your period & tender heavy breast. Could this mean pregnancy?

Not really but. You can always simply check a home test. Home pregnancy tests are very accurate. They are the same tests used in a doctors office. They can detect a pregnancy 7-10 days after conception. The best time to take one is when you miss your period. If you doubt the result you can repeat it in 1-2 days. If you were pregnant the hormone level would rise enough for detection.