Why is it so hard this time around 😔

My boyfriend and I have been trying for almost 4 months for our second baby and still have no luck. It was so easy with our first but I'm slowly loosing faith with every negative test I take.. Our daughter just turned 3 in April and we are both in our early/mid 20's. We've been wanting another baby for quiet some time but wanted to wait till our daughter was a little bit older so she can understand better, now I feel like we've waited too long and it's getting trouble some. Any other ladies out there feel like this ?