I feel so badly for you. It's tough enough managing a chronic condition, worse yet trying to start and find a career you enjoy.
I think what's most important to remember is you have to do what's best for your health. Continue taking care of yourself, and don't give up. Try again with the job you loved, or just keep looking and keep a positive attitude - something will come your way.
I'm fortunate that I'm a little older (36) and have been working for years. I've been able to establish myself and learn my job (software industry) well enough, that when I got sick a year ago, I was able to get permission to work at home 4 days a week. This flexibility has been such a blessing for me. For me, I know that I could not work (right now, anyways) if I had to stand all day, if I couldn't dart to the bathroom in a second's notice, and if I couldn't rest when needed. Those are my limitations and I'm thankful that I'm still able to work.
Maybe you can continue your education, even with online courses? And try to pick a career path where you will have flexibility to work part time, flex time, work at home, etc.