I'd say it's a Wonder Week too. The first is at 5ish weeks and his 'symptoms' sound typical of a WW. Babies also tend to 'wake up' around that time so that could be freaking him out a little.

Lots of reassurance and maybe try the slings again. DD loved being in the cradle position in a sling (her head next to my heart) so that really helped with WWs.

I hope the phase passes soon