OPK help please

Stacey • TTC #1 for 5 yrs. MFI & PCOS. Aug & Sept 2016 IUI — BFN ❌. IVF/ICSI•10/27 - 0 eggs. IVF#2 1/29 - Fresh transfer of two 5 day embryos. Expecting twin boys!! At 28w we found out Twin A no longer had a heartbeat 💔 Both boys born at 33w on 8/30/17. Maverick
So I tested on CD9 which was the 5th day after AF. It was a very close positive. Every day since it has gotten lighter and lighter. I am now 1 day from FW and there is barely a line in the opk. I have a 31 day cycle. Could I really have O'd immediately after AF or is it common for it to go away and then start again? First month using OPKs so I'm lost and worried I missed my real FW. Glow has always been spot on for AF. And will and opk eventually only have one line?