I am currently 5 days late for AF. Which, I have been on perfect 25 day cycles for the past year. Never am I late. I have taken multiple tests, all bfn. I was wondering if it might be because I've been donating plasma lately. I tried to Google it and the most I came up with , is the hcg hormone is in your plasma. Do you think that could be causing my negatives..like I'm not letting my levels go up high enough for a test???