Is the second harder to conceive?

I’m new to this, never posted before I’m usually just a quiet reader. But I’ve been extremely discouraged lately. My husband and I decided we wanted a baby a little over two years ago. BAM first try pregnant, healthy perfect baby boy. Fast forward to the present. we’ve been trying for a few months, nothing, I used glow last time too. Can’t help but wonder what I’m doing wrong? Should I worry? I feel selfish because I’ve been blessed with a child already but he’s growing up and I want him to have siblings.