Hello, Irregularity in menstrual cycles can occur due to many causes. Psychological factors like stress and strain, change in diet and sleep, thyroid hormone imbalance, serum prolactin level imbalance, poly cystic ovarian disease, etc can lead to irregular periods. Meprate tablet containing medroxyprogesterone is usually used to induce the withdrawal bleeding. Sometimes while taking the tablet menstrual flow can start. If your spotting gets converted into regular menstrual flow no need to take the remaining tablets. If the spotting continues as only spotting or subsides better to complete the course of the tablets. As your home test for pregnancy gave the negative result the possibility of pregnancy is less. Hope I have answered your queries. Let me know if I can assist you further. Take care Regards, Dr. Sree Gouri SR