My first years dealing with incontinence were in the latter half of college. It was tough. At that point, it would have been a disaster if anyone found out (or so I thought... thinking back there are some people who probably would have been very supportive but that wasn't where my head was at then). Essentially, you've got three challenges:
1) Making sure your inventory is not discovered. - I think this is actually the hardest of the three. There aren't a lot of places to put diapers that a snooping roommate won't find. I didn't keep a lot of diapers on hand. Just about 2 dozen (accidents for me were infrequent back then) and I'd replenish them every couple of weeks. I used a bag with a suitcase lock on it in my wardrobe. I could tell that someone once tried to get into it but couldn't (the lock combo was set differently than I always set it)
2) Getting supplies into your room - This is actually pretty easy. Just make sure your school backpack is big enough to carry the diapers you buy. Just like any other time you come and go with your backpack, you bring in your replenishment stash.
3) Changing - I think with the private bath, this will be a lot easier for you than it was for me with a public bath. My roommate was gone a lot so I'd usually change in the room. But with a private bath, you can probably just put the diaper in your shave kit and carry it to the bathroom. Then carry the used one out in the shave kit and dispose of it somewhere on campus. I wouldn't leave soiled diapers in the bathroom...
I'm pretty sure you'll be able to manage without being discovered. Just remember if you are discovered that a lot of people deal with this and that it's only a small part of who you are. You will find people who support you no matter what underwear you wear. Enjoy your fourth year! What a great time of life!