My husband is going through something very similar at the moment - his brother died suddenly aged 34 seven months ago. He was the gentlest, most selfless person we ever knew and it is horrendously cruel that his life was cut so short.
Like you, my husband is struggling terribly. This was his best friend, and the only person that has shared his life at every stage. He found this book useful:
SURVIVING THE DEATH OF A SIBLING: Living Through Grief When an Adult Brother or Sister Dies: T.J. Wray: 9780609809808: Amazon.com: Books
Sometimes he feels that people can't understand why the death of his brother has hurt him (and changed him) so much, as though his should be a lesser grief than that of a parent or a spouse, so he found the sibling grief book somewhat validating.
and he also went to talking therapy which was of some use I think, but the pain endures.
I can't offer you much advice, except to say that you will carry him with you in memory, and eventually you will find the strength to rebuild.
Good luck