I'm on only 50mgs of Seroquel and it knocks me out too.
I've noticed it also helps with my anxiety. Maybe it has to build up in your system before you see any help with the anxiety. When my doc put me on it he said it would help but I didn't believe him (because I know more than him, lol) My doctor won't give me anti-anxieties anymore either, so I'm glad this helps a little bit.
I haven't gained weight on it so far.
Good luck!