One day of spotting...

Hey everyone! So my cycles have been spot on regular for eight months since my IUD removal, 28-29 days. Usually I’m a moderate to heavy bleeder during my period. We’ve been TTC this whole time. My period was due two days ago and I spotted a bit yesterday. Nothing since. I took an early pregnancy test, supposed to detect pregnancy five days before your missed period, about three days before I was due to menstruate and it was negative. This is really abnormal for me and I’m unsure as to why I’m not bleeding. Any ideas? Has this happened to anyone before?