Wow

sounds like Brian's a hungry boy! It's possible that he has hit a growth spurt, and that this is temporary. I understand how exhausted you are though - this is exactly why I ended up cosleeping with Alyvia, because I personally couldn't handle it.
I think Tanya had the same problem with Rowan nursing for hours. I can't remember if they ever got it worked out though. My only suggestion is to try to hold out... nurse him as often and as long as he wants and pray that this is temporary. You might also want to contact his pediatrician to see if he/she has any extra tips.
I wish I could help you more than that.

Keep us updated, okay sweetie?
*edited for accidently tripping the profanity filter*