hello thanks for your query. If loads of tests are coming up negative, even you can surmise that you are mostly not pregnant. You should consult a gynecologist anyways to confirm pregnancy and also to know otherwise the cause of your irregular and scant cycles. The leading cause could be polycystic ovaries, as it causes delayed , infrequent and scanty periods. Other reasons could be anxiety, stress, emotional upheavals, frequent travelling, hectic work stress, ingestion of hormonal medications, weight gain or loss that is rapid. thyroid, prolactin and adrenal hormone disorders should be ruled out. endometrial causes, tuberculosis, anemia should be investigated. Take care.