you and your wife need to get thoroughly investigated as to what is preventing her from conceiving.That includes getting a baseline ultrasound
scan of pelvis to look for uterus-any fibroids, endometrial thickness, Ovary state of follicles.Next she has to undergo hormonal
tests like Tsh, Fsh,Lh ,prolactin
to see if eggs are being released normally or not.Then baseline blood investigations like, Hb,Tc etc,, to see blood status.Next a Hsg test is done to see if tubes are patent,
Meanwhile you will be asked to get your semen analysis
to see whether good number, quality, deformed/normal head etc..
Let us know.