Hello. I have been trying to get pregnant for two years now, can you a…

Hello. I have been trying to get pregnant for two years now, can you advise me on where to start? What should I check? I had an ultrasound, everything is fine. I got pregnant right away with my sons, then after six years of trying, I was in a spiral. I thought it would happen immediately, but unfortunately not. I am already 36 years old, and after two to three years, it will be too late.