What do you ladies think?

My husband and I had sex every other day during ovulation time and I have been spotting dark brown since Tuesday and my period was due yesterday (friday) and I didn't get it. Today (saturday) I'm still barely spotting and I am so emotional and crying for no reason. Lol I also have slight cramping and lower back ache. I took a test on Wed and got bfn. What do u ladies think? Could that have been a false negative and when should I test again? :)