Very confused...Help!

So I've been TTC for 15 months. This is my second month on Glow and first month bbt charting. Glow says that my fertile window was 3/7 to 3/12 and AF is due on 3/26. But according to my chart did I ovulate on 3/4?? That would make today 7dpo (i didnt record temp on 3/9). Today is CD18 and I had some very light spotting and my nipples hurt (like AF is on her way). Does anyone think that the spotting is IB? Or am I just crazy? Help!