@Kitty901 if you search through my posts on here I have posted about vitamins I've been taking and food etc. I don't know if it all helped but I was exactly the same as you, my daughter took 5/6 months and I'm now 7+2 weeks pregnant and when we got to the 6th month I felt like it wasn't going to happen, then finally it did. I did some research into it all and just decided to do what I could. I posted a photo with the post which might help you find it 😊 I wonder if my luteal phase was in the shorter side and lots of women talk about taking vitamin B6. Worth a try!
@Skylark1990 so glad the gp is sending you for tests, I hope that gives you some answers and you'll get a strong BFP soon xx