I am sorry you're feeling so down. I am surprised they are making you wait for the fistula to heal to start Humira, I thought humira helps fistulas? Have you considered seeing if there is another CR dr you could meet to get an opinion on the situation? Are you using any 5ASAs?
If you're really feeling bad, I recommend speaking to a professional. I did and I actually think the medication helped my UC. I am not sure if it is the medication or the better mindset but something helped.