Muscle Strain

i got injured at work. i pulled my muscle up by my rib and up to the shoulder. its taking alot of time to heal. i was taking a box down from a pallet and i lost hold of it and it pulled my arm all the way back as it fell. i have been on light duty at work for the past month and recently the plant manager told me that if i dont get healthy enough to get back to work soon that when i do get completly healthy that he will have to let me go. can he do this? i dont want to go back to work if im not completly healed. what can i do about this?

See your other post