Has this happened to you?

So, we have a 5.5 year old daughter and just started TTC #2 a few months ago. I will be 37 this year, so I realize things may have changed in my body since last time. I've been using this app and OTKs the past couple of months so I have a good idea of when my fertile window occurred.  So, my fertile window apparently started the day my period ended. Today, I'm maybe 5 or 6 dpo.  This month has been strange in that I've had *very* light spotting each day since my period started. I've also been pretty gassy - lol.  Anyway, this morning, my stomach was hurting to the point that I was almost in tears, and the spotting got a bit heavier. I still wouldn't call it heavy. It was just noticeable when I wiped. But that, combined with the cramps that calmed down after napping with a heating pad for a couple of hours, have me curious and a bit concerned.  I'm still very lightly spotting, but I'd characterize it as less than this morning... Nothing like a period.  Thoughts for me? My husband suggested that the two (cramps and spotting) could be unrelated, which I suppose is possible, but the combination raised a red flag for me...