How to bring up having kids?

My boyfriend and I have been together for just about 5 years. He knows that I've wanted kids since before we started dating. He also has said that he would like to have kids. While away for a work trip he wrote me letters talking about how he wants to marry me and everyone he sees me with my nephew he can tell how good of a mom am going to be and when he holds and takes care of my nephew he said he can't wait to be a dad one day. I'm not sure who to bring up that I'm ready now even though I'm about to start going through nursing school. He has said that he want to wait until schools finished but my biological clock is ticking as the older I get the high the chance of having an at risk pregnancy. What is a good way to bring up wanting to try and start put family sooner rather than later?
How to bring up having kids?
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