Just started LDR

My boyfriend and I have been together for over a year, and about a week ago he moved to another country for university. It’s not insanely far we can technically drive to see each other but it still feels like a huge change.
I’m really struggling with the transition.
One of my biggest fears is that he’ll meet someone new at university and eventually realize he’d rather be with them. He’s going to be surrounded by new people, making new friends, experiencing a completely different life, and I’m scared that eventually someone else could become more important to him than me.
I also have this other fear that honestly scares me just as much: that we’ll both get extremely busy with university and slowly stop having as much time for each other. Right now we’re used to talking a lot, sharing little things throughout the day, sending pictures, etc. But what happens when we’re both buried in assignments, exams, studying, and everything else? I’m scared that the less we talk, the more distant we’ll become, and eventually the relationship will just fade.
And then we did something that probably wasn’t the best idea for me
We calculated the total number of days we’re realistically going to be able to see each other over the next FIVE YEARS because of university schedules/holidays, etc.
13 days.
That number absolutely destroyed me.
Thirteen days of actually being together in person over an entire year feels so little when I think about it. And then I start thinking about five years of this, and it feels overwhelming.
I know we love each other. I know long distance relationships can work. I also know that five years is a long time and our circumstances can change. But right now, only a week into this, I’m having such a hard time adjusting to the reality of it.
For people who have been through long distance, especially when one person moved away for university:
How did you deal with the fear of your partner finding someone else? How did you keep the relationship from fading when both of you got busy? And did it ever eventually start feeling normal instead of constantly scary? Do you think there’s hope for us?