In the current scenario, it is unlikely that you are pregnant with so many negative HPTs. Yet, you should get a confirmatory conclusion through an assay of the serum beta-hCG
titres and a trans-vaginal sonogram. Weight gain subsequent to the use of oral pills
can also cause disturbed hormone profile raising the requirement and hence may cause delayed or absent periods. Please see a specialist for a proper appraisal of the situation. Hope you find this information useful. Take care.