I feel alone..

Okay me and my SO have been together a year and five months, were are not trying to conceive.. I've had hopes of being pregnant at some points but then flo comes. I see everyone around me not in a relationship not trying to have a baby and yet they are getting pregnant one after another some of my friends have 2-4 kids and I'm older then most of them I'm 21. I don't drink I don't smoke, I don't use protection I'm not on any birth control and i have never gotten pregnant.. Am I missing something? Is there something wrong with me?