If they are not hassling you to go back, then don’t go until you feel ready. Every injury is different. They are not paying you by the sounds of it so you have no need to feel guilty (in fact, they may even be happy about it if it is saving them money). However, you should find out if there is an occupational health person, because they should be managing your return. Otherwise, the driving goal sounds like something to aim for. Look after yourself.