Hi, Irregular periods are not a symptom of pregnancy. If you have previously had regular cycles, you should suspect some hormone imbalance. If you have a missed period, you should perform a home pregnancy test 3-7 days later with a fresh early morning sample of urine. If, as you have, repeated tests are negative, you are mostly unlikely to be pregnant. Yet, a trans-vaginal sonogram and a clinical evaluation help to clarify the issue. If pregnancy is thus excluded, further investigation should help to identify the cause of the irregularity. Please maintain a healthy weight, regular exercise and a healthy diet. Take care.