9 days late but neg blood test! Ugh! Why?

Hubs and I have been ttc for 3 years and finally have a good infertility dr. Everything is good with me but his count is low so he is currently on clomid. This was the first month we got to try with it. I have a 28 cycle latest I have ever been is 2 days late. I am now currently 9 days late. Went for blood get on day 7 and it was negative! I'm sooooo confused! Tiny spotting this am and then nothing! Dr said I can take a med to make me start so we can try again while he is still on med?! Not sure what to do.... Will this mess up my cycle? Wish I know why I am so late! This is soooo not normal.... Has this ever happened to anyone else?