Help! TTC, What do you all think of this??

My husband and I have been TTC only for about 2 months now, we've been having sex on days we are most likely to conceive. My last period was very light, not red at all, and now today I just started having some cramping and very light brown spotting, my period is not due for another week. Here is a screen shot of activity for this month. Please help explain??? I can answer any questions I just need to figure out what the deal is. TIA!