Frustrated, confused, and lost

It is very frustrating to me that I just learned my ex and his new girlfriend are expecting twins and although we were not TTC together we also did not use any form of contraception. And now I’m eager to start a family with my fiancé and nothing is happening. It makes me wonder if there is something wrong with me and that’s why I can not conceive. I try not to get bummed out or stressed out and just trust that when the time is right I will be blessed by its very hard