opinions on vitamins, please!

so I'm coming up on my third month using these; vitamin b12, nettles, prenatal with dha, and vitex. I've been getting positive opks so I know I'm ovulating, but I was getting my period again and now this month it's mia and bfn, so obviously my blend of vitamins and herbs aren't working. my question is should I switch it up and what have you had luck with as far as vitamins and herbs with getting pregnant, one week before I'll be ovulating again, so help please! ordering pre seed and premama this month also..