With all the confusion in the current situation, the best thing to do is to go for the assessment of the serum beta-hCG
titres as the best method for confirmation/ exclusion of pregnancy
. The use of the emergency pill during the last cycle could alter the hormone status of your body and this is another likely cause for the menstrual disturbance. Potassium tablets cannot alter a menstrual cycle; an infection can, of course disturb it. Hope your query has been answered. Wish you good health.