Hi Pitrof, Welcome to the forum. Congrats on finishing high school. Tho I am not a college aged individual, I understand your concerns. But I think you have to set a priority list. Getting into uni, and finishing... IS an important and worthwhile goal. However, your FIRST responsibility is your health. It has to come first. Your doc. HAS to be consulted... you'll need a working drug/personal regimen to enable you to tackle uni.. If pred. is off the table because of how much/long you've been on it, then he/she has to provide you with alternatives.
The train ride sounds daunting, but I think if you prepare for it before hand, and scout out the loo locations at the station and on the train (hopefully there is one) then you should do OK. You don't say where you are from, but if it's in the UK, think our UK members can tell you about getting a special key to loo.
As for telling your teachers, my stance would be an overwhelming YES. you've got a real challenge to deal with, and it is going to present unique situations. I would advise all of your profs/instructors that you have this condition, and that you are going to endeavour your best to cope with it while in university, but it has a mind of it's own, and when push comes to shove, it really calls the shots. (Notice how I spelled that, so tempting to mis-spell it - dont' get me wrong, I'm not making light of your situation, but I usually try to see the humour in "OUR" situation, OK? Just one of my methods of coping, but then again, I'm a looney).
Eating... That's a trial N error situation for a lot of us when it comes to eating outside the home. Pack a lunch, lite snack, to tide you over. Try the food there, see how you make out. Given time, you'll probablly learn/adapt to college fare.
If you've advised your teachers, then see if there are guidance counselors, etc on campus .. health nurse, etc.., who can advise you on this. Think you'll learn that you aren't the 1st student they've had with this ailment, and they'll likely already have some things in place to make your transition to college easier. It certainly doesn't hurt to ask. And in the extremely unlikely event they don't, it is as good a time as any for them to tackle the issue. you're a student, its their responsibility to put measures in place to assist you in this. don't settle for less
Think that pretty much covers most of the points you raised. I'll address one I think is 'between' your lines. Think that you are compounding your fears, and letting them grow out of proportion. not that the concerns you listed are in any way ingenuine. they are all real. But, like any group of concerns, if you lump them all together at once, they can seem overwhelming, even insurmountable.
that's not the case.. you just need to break them down.. tackle them one at a time.. reduce them to a 'manageable' level you can cope with, with your health issues. You can do this. worst case scenario, you have to compromise, maybe take a little longer (with health considerations/interruptions) longer than your peers. Big deal. do you want to get thru uni.? think you do, else why go, right? Life throws a lot of obstacles in our path, be on your own side. Don't go putting any in your path... if they are going to surface, let them do it on their own. OK, enuff of my long winded ramble. welcome to the forum, all the best.