Having trouble getting pregnant after having 2 kids my husband is 40 with 1 child I'm 21 with 2 why can't we conceive?

Get checked out. I am guessing you had no difficulty getting pregnant before. I recommend seeing a fertility specialist (rei) to help you to get pregnant again. We check you for ovulation issues like pcos, other hormonal problems, low egg supply, blocked tubes (did you have a c section?), problems inside your uterus or sperm problems for your husband. We find a sperm problem almost half the time.