Ttc baby number two but three days late and negative hpt also have hypothyroidism

Patient: I am 22 and ttc number 2. I have hypothyroidism. I am 3 days late and im never late. im not under any unusual stress. I took 2 different hpt and they both came up negative. could my having hypothyroidism be causing it to show up negative? I had mild cramps about a week and a half ago and feel a tad bit nausea. I am only on 25 mcg of the levothyroxin once a day. could it be possible that with the thyroid issue it may take longer for the hcg to show up positive?