Hashem is not punishing you for making fun of disabled people. Hashem has a master plan for you and your job is to do the best you can to serve Him with whatever He gave you. Perhaps this realization is an opportunity for you to do a full tshuva for those hurtful actions. Many of us will not even remember things we did and we will go without doing tshuva for them.
I spend a lot of time with people with Autism and I think they are awesome people who are closely connected to Gd. I agree that you should find a therapist or rabbi who councels who can help you see your true worth.