Please check partner's semen analysis. If it is normal, you are ovulating regularly and your tubes are patent and regularly trying for pregnancy for 2 years. If still not able to get
pregnant , we call it as unexplained infertility and iui maybe very less effective for such cases. IVF/ICSI is the treatment for unexplained infertility but has a success rate of 33% per cycle +/-10% depending on various other factors