I might be jealous

Ok so my sister got pregnant at a very young age and has a set of twin boys. We Dont have twins in our family NOR does the father. The father has been in jail since they were conceived, but that's not really my problem. I might be jealous because I have been trying for a few months and its on the days I'm supposed to be "fertile". J and I Dont have sex very often but when we do it's out of this world. I'm 23 I'm ready for my own family , house , kids , and him to be my husband. We've talked about this topic multiple times. J and I have been together for 5 years and I just wanted to know if I am going myself into something real or no.