Going from 3 to 4 ?

I have an appointment next month to get my iud removed. We have 3 boys! We have always talked about having 4 kids, rather close in age. We went from 1 to 3 ( had twins!) they are 19 months apart from their big bro! I love how close they are. 1 to 3 was hard for me. I’m a little nervous to go from 3 to (hopefully only!) 4! This will be our last and id like it to happen before I’m 30! ( I’ll be 28 in a couple months!) any advice from going from 3 to 4 or insights? Thanks!