Hi Irregular period could be due to hormonal imbalance because of changing of birth control pill. I would suggest to wait for period. If period will delay by more than 14 days from expected period date, consult the gynecologist for detailed examination. for investigations of irregular menstruations. You may be asked for hormonal work up like FSH, LH, Oestrogen, Progesterone, Prolactin, etc. Before hormonal check up, you will be examined internally to find any organic disease like infection or cyst-Ultrasonography also will reveal a good amount of information regarding your internal organs (and even pregnancy also). Avoid stress, take healthy diet, drink plenty of water and do regular exercise. Hope I have answered your query. Let me know if I can assist you further.