i reckon the 6 week mark is a doozer. i remember it with DD1 well....and that was 3 years ago...lol.

sounds like it could be over-tired stuff too...which is really common and very easy for a young baby to become. with dd during the day we would pop her in the pram swaddled up and rock the pram or use a rug to 'jig' it until she settled...sometimes a bit of a pain, but did give the arms a break and helped me recover from the stress.