Want to give up

Kathryn • Hello everyone, my name is Kathryn and my fiancé and I are trying for baby number 2. We have a 4 year old daughter
I honestly feel like giving up! 2 years on and off trying and on month 3 of constantly trying and nothing yet. Yes I have been blessed with a beautiful daughter and I'm lucky to get the chance to be a mom and everyday I'm thankful for that..but I don't get it!! Why aren't we getting pregnant??