Spotting for 10 days

I have a almost 14 month old and am ttc again. My "period" was 4 days late and Ive been spotting on and off for 10 days mild cramping at the beginning but none now. my boobs are pretty sore and I'm tired. Took a test this morning BFN. Anyone have any experience or advise? I've had pretty normal periods since about 4 months post pardum.