Not sure what to do, any advice?

Hello Everyone,

First off I’d like to say that I’ve been in a relationship for with my fiancé for almost 6 years, we have 2 kids together, and I have 2 from a previous relationship. I recently turned 30 and our youngest will be 2 soon. I have always expressed wanting a big family and he’s always said he did too. I keep telling him that I think I want one more child, especially since I’m not getting any younger and my family history of having issues of having children at older ages hasn’t been the best. He acts like we have all the time in the world and I don’t think he takes me very seriously... I make sure he and the children are happy and have what they want, and I honestly feel like it would complete my desire to have a big family. How should I talk with him about it? I try to be more serious and express myself with valid purpose but I feel like he just doesn’t get it... I just worry about it a lot and just feel incomplete... I’m just looking for some advice and maybe someone who can understand how I feel... thanks so much for your time and consideration :)