Ttc postpartum no or late O

Hi guys I have 3 older children 19,17 and 14 from my previous marriage and an 8 mth old with my hubby I just got my period?? Finally 14 days ago it lasted 5 days but was lighter than normal and mostly brown (old blood). Anyway I always used to Ovulate on CD 13 or 14 so started using opk strips starting cd10. Have had a few very light lines but nothing close to positive and now cd14 with an even fainter line. I took a pg test yesterday incase somehow I was pregnant. It was in the afternoon after a short hold and came up bfn.
Came back a few hours later and saw a definite line which I'm assuming is an evap line? Anyone else with experience in late or no ovulation on cycle after first period postpartum??