Jealous and Depressed

Chasadey
I'm 31, my husband is 30 and we have been TTC for our first baby a little over a year now. My husband has 3 kids. 2 from his previous marriage and 1 that he had when he was only 15yrs old. Well the child that he had when he was 15 yrs old is now 14 and forgive me for being jealous but is actually expecting a child of his own in June!!! Am I wrong to be jealous?