How do I (20F) stop nagging my (22M) boyfriend about proposing?

Hello everyone. I know the title sounds a bit cut and dry, but allow me to add some context. I’m currently in what social media has coined as “engagement purgatory”, and I’m going absolutely insane.
I have always been a snooper. Christmas, Birthdays, or anything of that nature. Honestly, it’s always just been part of the fun for me around holidays. My boyfriend is well aware of this, and has expressed his frustrations with it in the past.
Now here’s where it gets a bit more complicated. As you saw in the title, we are incredibly young. I am currently a junior in college, and he will be receiving his degree later this year. We both are pursuing engineering, and have very good heads on our shoulders. We’ve also been together for 5 years now.
Personally, I’m looking to get engaged next summer, and hopefully married the fall following my graduation. I’m from a very small rural area, and will most likely have to move very far from my family in order to fulfill my career. Because I’ll have to leave my hometown, I’d like to plan the wedding close to my family while I’m still around. Planning a wedding from a distance also just sounds like a nightmare imo. My boyfriend and I also have grandparents that we would like to be there. So all of these factors have come together to give us our general desired timeline.
Now, as to why I’m nagging.
In a very blunt way. I don’t necessarily trust him to plan it. He is a known procrastinator, especially when it comes to things in our relationship. For our 5 year anniversary, I told him months in advance that I’d like a professional photoshoot as an anniversary gift. I gave photographer recommendations, and monthly reminders. Mainly because I’d be the one picking the outfits and don’t necessarily think a gift like this should be a surprise. He put off messaging a photographer until the Tuesday before our anniversary (on a Friday), even though we had several fights where I got on to him for procrastinating it.
For my birthday this year, I hinted at really wanting a surprise birthday party with my friends. I have a summer birthday, so I never get to celebrate with my friends from college. I thought it would be nice to have a party during the school year, no where near my actual birthday, to celebrate. My boyfriend took my hints and decided to plan one for me. I knew almost instantly when it was happening, but I didn’t have the heart to tell him that, because he was so proud of himself.
It wasn’t until the after party debrief that I figured out, he did absolutely none of the planning. He mentioned it to all my friends, then procrastinated planning so much that my friends made the group chat, picked the date, and made up the fake scenario for it to be a surprise. The only things he did, to my knowledge, was give them an idea of the decorations and food I wanted (which I fed to him because I was suspicious of the party). He also ordered and purchased the cake.
These are only two recent examples but I have countless more of him just not being able to plan and prioritize things without someone walking him through it. It’s been the source of several arguments.
As for the engagement, he has people like his mother to help him plan it, but I want him to plan it, not his mom…
So when I’m nagging, I’m asking questions like, “Will it be within the next year?”, “Have you planned it out”, “What did that person think of your plan, and did they think I would like it?”.
He says that the proposal is his thing, and that I’m ruining it for him by asking questions. I obviously don’t want that, so I really just want advice as to what I can do to calm my nerves about this. I just want it to be special, thought out, and in our agreed timeline…please help.