I am 39 years old, My cycle is very regular 27 or 29 days long. I am currently currently a week late and I have take 3 HPT and one urine test at the doc all negative. However I am having other symptoms of pregnancy. I am tired, moody and queasy quite often. I have never been pregnant before. I had my thyroid completely removed last year and I am taking a daily does of 112mcg of Levothyroid, Can the test be wrong? If I am not pregnant what else could cause me to miss my period?