Implantation bleeding or ovulation??

Sorry this is all new to me what I'm experiencing. I have pcos and I'm TTC. I had my period Dec 18-21, and I've been cramping on and off since the last day till now. On Thursday of last week some brown discharge and on Friday I noticed brown discharge and when I checked again there was a little bit of pink and red blood. Friday I felt light headed, nauseas and cramps. Saturday, Sunday, and today I feel nauseas, tired and have cramps. My AF is just around the corner. What could it be?