So confused???

Kristen • Ttc#3. Currently have a 6 year old daughter and 19 month old daughter. Married to my husband may 2014.
I think I may be out. This past Friday I had really light spotting in the evening it only lasted a few hours. Sunday it was back in the morning and lasted most of the day but was gone by around 7pm. This morning it's back again but it's more than before but still not heavy like a period. Does anyone know what this could be? I'm estimating my ovulation last Thursday so today would make me 4dpo. I didn't temp so I can't be exact. I did opks never got a positive but it got really strong for 2 days prior to o then strong negative. My last af was July 1st-4th