is ruled out since your urine and blood pregnancy
tests are negative. Other causes of delayed and irregular periods are hormonal fluctuations, high levels of stress, extreme changes in weight, chronic anxiety, ovarian dysfunction, thyroid hormone imbalances. You need evaluation for above mentioned conditions. A hormonal assay, thyroid function tests, pelvic scan may help in diagnosing the cause of your symptoms. Consult a gynecologist.
Best wishes and regards!