Time to grow up

So my fiancé and I have been together for 4 years. He is 23 and I'm 22. We went through college together and have grown a lot together. I've always been more mature than my age and my fiancé knows this about me. He works hard to be mature and grow up but sometimes his immaturity shows through. I know we met at 18 and 19 so he's obviously much more mature but sometimes I'm worried he won't grow up. I'm also worried I'm pressuring him to grow up before he's ready and he'll resent me for it. I've talked about all of this with him and he reassures me not to worry and he wants all of this with me. And that he is working to grow up and just be patient with him. I love him and I know he loves me. I guess I just needed to vent but if anyone has advice I would welcome it!