I am sorry to hear of your difficulties.
Look in your community for adult education classes. (You will often find these through your Parks & Recreation department.) They usually offer G.E.D. testing for which you do not have to first take classes - you just pay the fee and take the test whenever it is next scheduled.
I believe that will be your best bet to get it done quickly.
P.S. It is my understanding that the G.E.D. test may be more difficult than the coursework necessary to earn a diploma. Should you find that to be so, you may wish to obtain a copy of your high school transcript and then proceed to complete only the missing credits you need, rather than spend the time and money necessary to earn the G.E.D.
Good luck.