I'm sorry about
your diagnosis. You've had a rough introduction which would make somebody twice your age depressed. I'm hoping that the Humira will put you in remission and you can get on with your pre-Crohn's life.
Don't fret too much about
diet. There's a lot of shysters out there who claim you can heal Crohn's with diet. You can't. Just do the best you can and don't beat yourself up for eating the 'wrong' things. Eventually you'll find the diet which works best for you in minimising symptoms, but in the meantime you can't make the actual disease itself any better or worse.
As depressing as this may sound, Crohn's will eventually become your new 'normal'. If you're lucky that normal will be pretty close to your old life (if never exactly the same); if not, well, you will still adapt anyway, because people do. You will probably better appreciate the good times than people who have never known what it's like to be sick or ill for a prolonged period of time.
As to why
the Crohn's happened, it just did. You drew the genetic short straw and were so prone to getting Crohn's when the conditions were right. Even if you had known you were genetically susceptible, there is little you could have done to have prevented it from happening.
The depression will get better. Don't give into it completely, but don't try to fight it too strenuously either: it's there for a reason. But if you think it's reached a point where you can't cope with life anymore (e.g. you're skipping classes or work, avoiding people, having suicidal thoughts, constantly numb or crying etc.), then go to your GP.
Finally, if you've got any sympathetic family members or friends, then do talk to them. You shouldn't have to face this all alone.
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)