ALL opinions welcome!!

Athena • Pregnant with baby #2 (#1 = angel), 31yo, DH 34
This is my 2nd month tracking w/OPKs. Last month I had a 14 day luteal phase. This month I am due to start AF in two days (Nov 4th) which would be 13DPO. HOWEVER, I had heavy spotting yesterday. If it's AF, my LP shortened by 4 days?! Has anyone experienced this? Is this still considered "normal"?