Even once you're ready, looking forward to it, and can barely wait for it, becoming pregnant can sometimes be a bit of a waiting game. When everyone around you is falling pregnant and telling you "your time will come, too" all you can do is cross your arms and wait.
Amongst other things, medical complications can really throw a spanner in the works. For example, after a molar pregnancy, if you are in rehabilitation after an accident, or are on certain medication, can all affect the time it will take to fall pregnant.
From Cassandra-Harmon In Q&A