Surgery to deltoid muscle - how long will it take to adapt? I'm quite upset by how weak I am at the moment.

Can anyone tell me how long it will take to adapt to surgery which has removed most of my deltoid muscle?  My surgery was almost 1 month ago and I am keen to know when I will be able to drive again.  I tried changing gear today but do not currently have sufficient strength to change gear.  My physio is starting next week.  I am quite upset about the level of weakness that I have.