Say we had sex a day before her period was due, then it came a week late, now a month later it came but it was late again is she pregnant?

Unlikely: If a woman has her period one week late, but it still looks like her normal period, then she is not pregnant. However, any couple who is having sex must accept life's surprises, such as a cute little baby... meaning be ready to be married, settled down, and raising a family. If worried, one can do a home urine pregnancy test. They are very accurate 3 weeks after sex, and are sold everywhere.