Talk to Gynecologist on Missed Periods

AOA respected drs I am married for last three months. My cycle was regular before marriage. I used to get periods on every 30th or 32th day of the cycle but now I haven't got periods yet. LMP was 18th march and it was also of 35th days. I have done strip test couple of times but got negative results. Even though I m having symptoms that are quite different from PMS like having extreme fatigue and metallic taste all the time along with body pain. I had light spotting on 33rd day of the cycle and it was brown in colour I thought periods have started but after that I haven't got them yet. Please guide me what should I do