Please give me your input!!!

So my ovulation day was 1/21, (I had a positive digital ovulation test), which is 8 days ago. My period is supposed to start 2/5 according to Glow. I have been having really serious cramping and back pain. My nipples hurt!! Not the whole breast, just the nipples. And they get hard a lot lately. Could this be implantation or the starting symptoms of my period?

Vote below to see results!