why it is so difficult to get pregnant ?

Why it is so difficult to get pregnant naturally? It's been more than a year . I am so depressed. Had all the tests even Hsg too . 2nd cycle after HSG passed . Trying everthing.Still no success. Those who dont want get the baby unexpectedly and having more than 2 are still so lucky . Why the ones who want it so desperately are suffering. Ttc baby #1. I couldn't think myself without a baby in future. I can't wait any longer too. How people tolelerate this waiting trauma for more than 3 years. Saw many people online still trying for 5 years , 10 years. I can't even think to place myself in that position. Why is it so hard ? I am sorry but i can understand how they are going through this.