So that's my first suggestion. Don't try to DIY your post-partum journey. It isn't the same as a regular muscle, joint or even disk injury. Your pelvis may not have stabilized, your abdominals haven't recovered from pregnancy, and your posture hasn't recovered. Instead of a quick 2-4 week recovery, I spent 8 months frequently in too much pain to turn over, wincing when I lift 20 pounds of baby, and with a stabbing pain when I hopped down out of our car.
I very strongly suggest working with your pre-and post natal medical team postpartum. Shoulder, back, neck, hip, glute and arm injuries are common, and most new parents don't have the energy to work on themselves. Even your regular RMT, physio or acupuncturist may want to take extra training to strengthen their knowledge of how your body knits itself back together post-partum - it's just as incredible as the journey of pregnancy itself.