First let me assure you that you don't need to have a period to be healthy. Sometimes you may miss a period or more because you are not ovulating for some reason. Sometimes it is due to stress or perhaps a hormonal problem such as PCOS or thyroid disorder. The weight gain is also often associated with hypothyroidism so a good overall exam would be indicated to address all of your concerns at once - absent periods and weight gain, along with any other complaints you may have.
The answers in online forums are for information only and are not intended to substitute for medical advice and care. Please see your personal health care provider for further evaluation of your individual case.
Debbie Miller, RN