Opks and conception

We have been trying for 6 months now using OPKs and still nothing. We already have 3 beautiful littles 2 of which were not expected. I remember it taking us a year to have my daughter that resulted in 3 miscarriages… I remember going to see the fertility specialist before and at that appt actually found out I was pregnant with my daughter and never had to follow through. Do you think it’s worth going back since I’m getting positive OPKs and nothing is happening? I have very long cycles ranging from 27-40 days.