Ovulation?

New to bbt so looking for some advice. 
TTC 4 mths after having nexplanon implant removed.  Cycle returned immediately and is 28/29 days. 
For last 3 cycles temps similar to below.  Ignore first spike at cd5, I had a cold.  I thought the spike incd15 may be ovulation but temps haven't stayed up.  cd19 stomach aches, back ache, tender boobs, like AF was coming.
cd20 brown spotting, turning brown/red later. cd21 now and still there. Not implantation bleeding as happened for last 3 mths and normally last 2-3days.  Is this a second AF?? 
Any help is appreciated x

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