Hi there,
I hope I can shed some light into what's going on.
First off, big hugs to you! You are in the toughest part of changing a sleep habit, what I refer to "in the thick of it." Because he's an older baby, and is used to being mostly rocked to settle down, he's reorganizing how to fall asleep.. relearning it. Typically, it takes an infant 3 weeks for their circadian system (body clock) to adapt. In this time, you going to have challenging days and awesome days. Kinda like two steps forward, one step back. This is normal, and it's my fault, I should have warned you about this.
It does take time and patience.. and a support system, but I encourage you to keep at it. It will get better, and i know right now, you don't believe me!! (don't worry.. I've been exactly where you are, with my first son!)
Big hugs to you and hang in there! Take it day by day!