TTC Baby #3 Any Advice Will Help Please!

My Fiance And I Are TTC. He Has One Child Previous And I Have Two From Previous. All Three Dying For A Little Brother Or Sister. We Have Been TTC For 11 Months Now. I Have Gone To The Doctor At The TTC 6 Month Mark And She Told Me If I Didn't Conceive Within Another 6 That We Would Discuss What The Next Step Is And Get Me Started With Fertility Meds,This Appointment Is Coming Up Next Month. I Am Currently On Similac Prenatils,We've Used Tubes Of Presseed,I've Stood Upside Down,I Eat All The Go To Foods For pregnancy,Non Smoker,Non Drinkers And I Just Don't Know What Else To Do...I've Had Over 20 Negative Tests And Its Just Starting To Kill Me.