Spotting neg HPT

I have a question for you all. AF was supposed to come today cd28, I have been spotting (light brown) since cd21. On cd 26 I had some really sharp cramping in the am (about 2 hrs) and then felt like I was getting AF. I noticed some brighter red on the tissue paper and assumed it was AF. But it turned out it was not. So it is Cd 28 for me, still brown spotting, cramping, and took a HPT which was neg. What do you think, anyone had this problem? Oh this is my second month on clomid and I had a + OPK on cd 16 & 17.