Mtln, maybe you should ntnp and just let it happen without all of the testing, temping and opks. This seems to be taking a lot out of you, adding a lot of stress, and taking you away from your kids. Testing, temping, and opks don't make you conceive...they just are tools and tricks to make women go crazy. You already have kids, so it's not like it won't happen again...just relax and let natural take over. Trust me. I think trying so hard is actually stressing your body out to the point it's keeping a baby from sticking.
Drink a glass of wine, enjoy the holidays and you will get your baby soon. Promise