So confused

Hi all, I'm so confused.

My son was conceived over 5 years ago whilst I was on the contraceptive pill, so was a massive surprise to us. He's now 4.5 years old and we have been trying to conceive since October last year with no luck.

I just don't understand why it was so easy to conceive 'by accident' the first time round (not that my son was an accident at all) but now we're struggling to conceive a 2nd child. I'm only 27 and relatively fit.

Has anyone else ever had this, and how long did it take you to conceive?

Xx