Brown discharge a week before period is a pregnancy symptoms ?

Had my anatomy scan today & everything went well! About an hour later I was having a little brown discharge which has happened before a few times this pregnancy. Anyone else have this happen to them?

So my period ended 3 days ago. Because I have pcos it says ovulation happens tomorrow, me and my fiance BD 3 times two days ago now I'm having dark brown bloody discharge, I'm wondering could this be my period coming back or is it ovulation bleeding? I've also had an awful head ache yesterday snd day before and woke up with awful nausea. I know it's not pregnancy obviously but never experienced this before.