I'm so confused

So I have 4 kids and you'd think I'd be a pro at knowing my body during pregnancy by now. I'm completely freaking out because I am having light red and brown discharge. I have irregular periods so I'm not sure if its the beginning of my period, implantation bleeding (which I had with all 4 of my others) or something else. My youngest is only 2.5 months old and we have honestly only had sex twice since he was born. But I think the last time (Aug 16) was during my ovulation or near it. Since I'm irregular it's hard to really pinpoint but I usually get frisky around my ovulation. We used protection and to our knowledge the condom didnt break but we also conceived our 3rd while using protection. I'm not upset if I am just scared because my youngest is still so young and we wanted to wait to have another until he was older. Has anyone had the brown and pink and not been pregnant?