Period advice

My period is officially 12 days late. I took a test on the 5th and 7th day that it was late, both came up negative. I’ve been under some relationship stress lately that has been effecting me both physically and emotionally (I’ve lost some weight). I was wondering if this due to stress due to the negative tests or if there’s a possibility they could be false negatives? Would it be best to go to the doctors to get the answer?