Have you tried anything to calm down oversupply? Like block feeding? Also, have you tried doing breast compressions while you are nursing to get your baby to eat more while actually on the breast?
What you're describing sounds exactly what happened with my first, somewhere around 7 weeks. She nursed constantly, was very gassy and very unhappy. She had green stools, and you could actually hear the gas rumbling through her poor little system. Once I started block feeding things evened back out, she was happier and her stools returned to a yellow color.