If you haven't done so already, please consult with a medical professional or physical therapist and have them explain what movements should be modified or limited. Anytime you are feeling pain or discomfort, it's best to listen to your body and rest as needed.
Modify your moves
If you feel like you can do some arm movement, only raise as high as your body permits. You don't want to push through any sort of pain which could lead to further complications.
You can modify planks by having your knees on the floor so there is less pressure on your shoulder area, and focus on diaphragmatic breathing to engage the core.
You can also start without our upper body equipment such as the hand weights or p.band until you can move without pain. When adding equipment, keep your range of motion small and go slowly to activate the proper muscles. Rest as often as needed as you rebuild your strength.