[not a doctor] intramuscular injection of marcaine and cortisone really helps me to stop the cycle of pain/awkward posture because of pain/more pain from awkward posture so that I can do my physio exercise and reduce pain in the long run. It's an option you could discuss with your doctor but continue to perform the stretches as directed. A few weeks probably isn't long enough to see considerable improvement - gotta be consistent with it.
Try this out: log your pain every day for 4 weeks (use an app to make it easier on you. You could even use daylio and use the 5 emotion faces to translate into a 5-point pain scale) so you can get a more objective idea of how your schedule, daily activities, and treatments are affecting your progress. Valuable tool for your doctor to get an accurate idea of what you're going through too. In my experience physicians are super psyched to get this type of diary (especially if they didn't have to nag you for it, you offer it up front) haha.