Hi, My Husband And I Have Been Trying To Conceive

Hi, my husband and I have been trying to conceive for about a year. I have 2 other children already. After my daughter was born my periods started being very regular, every 29 days on the dot. Every once in a while at the halfway point of my cycle I have my normal increase in fluid discharge and then get a little crampy as if my period is going to start, and then I have a tiny amount of blood when I wipe mixed in with the discharge. It's not even enough to be categorized as spotting in my opinion, it only happens once and then nothing else. What is this blood and cramping and what does it signal as far as us trying to conceive?