Hi!
I am sorry to hear that you are experiencing such intense symptoms at such an early age. I consider myself very lucky in the sense that my university years were not greatly affected by AS. I was diagnosed in November 2011, half a year from graduation. The summer of 2011 was when symptoms really started, mostly with incredible fatigue and intense pain in the SI joints. I graduated in the spring of 2012.
Ever since I was diagnosed, life has been an ongoing struggle. I am 26 now, so not that much older than you. I have learned to cope a lot, but as a young person it can be difficult to stop burdening yourself with unnecessary expectations and comparing yourself to others. I still do that a lot. Once I would have energy to do school, training, job and weekend parties and not blink. Now I get sleepy at work and am lucky if I can keep my eyes open when I get home from the office in the evening. So I compare myself to my past self as well as others and get anxious. I tend to run bad scenarios through my head like losing my income, home, girlfriend etc. It's there all the time and yet as the years have progressed from diagnosis to fatigue to back pain and the first signs of stiffness, I have also felt something akin to "coming into my own" or slowly becoming my true self. It has forced me to learn a lot about myself. The challenges I have overcome despite my condition and the help I have experienced have affirmed my faith in God and the goodness of other people.
In trying to overcome the disease, I have benefited more from self-observation, critical thinking and personal research than the help of doctors. Things that have helped me include:
*) Skipping breakfast - I have tried the no starch diet and noticed little difference in my own case. What instead works for me is intermittent fasting. If I couple this with calorie restriction (meaning normal portions for lunch and dinner instead of compensating the lack of breakfast with a doubly huge meal later in the day), it gives a marked reduction of morning back pain and increase of daily energy levels. This might not be for everyone though, so you just have to figure out what works for you. Nevertheless, I am completely convinced by my own experiences that it is possible to control the inflammation process with changes in diet.
*) Breathing exercises to increase body oxygen - Fatigue appears to be related to the amount of oxygen available for metabolism. I tended to and still tend to crash heavily after meals. One thing to try is to increase body oxygen. It can be done simply by performing aerobic exercise (runners and cyclists have bodies highly efficient in oxygen uptake), but this can be very difficult if one is completely exhausted. The problem can be solved by practicing breathing exercises at home. I use something called the "Frolov breathing device", a kind of a plastic tube where you put water in and then breathe through the water. The resistance of the water trains the body to breathe correctly. Usually right after an exercise session, I feel energized and ready to take on any task. Although doing the breathing is kind of tedious, exercise sessions usually last around 30 minutes a day. You can find more info on correct breathing at -
www.normalbreathing.com*) Training - both strength training and aerobic training are really important. This is also the hardest part for me. Because fatigue is such a big part of life, recovery periods tend to be especially long. I can only suggest taking things real slow. It is especially good to have a motivating coach or physical therapist, but even as little as 10 minutes of exercise a day can make a big difference. The most important thing is to keep at it. I have had to restart my exercise regime countless times.
*) Simplification - this is a philosophy that I try to carry forward in life. I try to keep things as simple as possible. This means that I always try to develop my own simplest method of doing things. I try to develop in my mind the capacity to approach each and every task with the question: "What is the simplest, most stress-free way I can accomplish this?". An example would be training regimes - there may be those who say that you have to do this or that many reps of this or that exercise to achieve results. What I found out quickly was that no one has the right answers for you. You just have to start trying things and in due time you'll instinctively develop methods that are most suited to your preferences and capabilities. In this way your abilities develop naturally and you don't have to worry about meeting someone else's preset standards. In any task in any field you have to start somewhere, of course - usually with a book on method - but whatever you are taught, always keep an eye out for possibilities to modify and most of all, simplify.
And I hope you feel better soon

Best
Artur