I know IB isn’t common but...

I think that’s what I’m experiencing now.. yesterday I had dark brown discharge so I thought it was the start of my period (although a few days early). Put a pantyliner on and went on with my day but there was nothing else by the end of the day. Put a pad on before bed just incase but when I woke up it was just a tiny bit of rust coloured spotting. Throughout the day just random spotting on my pantyliners, nothing really when I wipe. (Sorry for TMI) I’m nauseous, itchy sensitive nipples, dull cramps.. We aren’t TTC but we aren’t preventing it either (happens when it happens kind of attitude right now) so I haven’t tracked much of anything. Any ladies with experience in IB? If so, when did you test?