What good news! You should receive back pay from SSD - I am almost positive you will. Just beware - they take a big chunk of taxes out of the back pay when you file at the end of the year. Be sure to keep money aside for that "surprise". It can put you in a higher tax bracket from that much money in one year. However, it is still worth it in the long run.
You are young so it is fortunate you received it. This also makes you eligible for medicare. ( I think) Perhaps you already knew that.

Anyway - I am happy for you.
By the way - I adore your pictures of your dogs. I love animals and am involved in many animal welfare groups. My dog is from the shelter as are all my animals for 40 years. Pets are always such a comfort especially when you are disabled and can't get out very much.
Best wishes,
Sydney