I was in a car accident and need some advice?

i hit my head got a minor concusion. i am seeing a lawyer and everything as well as my insurance company. well i am kinda spacey and dazed and im really not feeling up to working right now, i have a note saying i had a concusion. what i want to know is if i take off a few weeks from work until i can get better if they can fire me especially since im part of the union. i have also missed a lot of work lately i had bronchitis before this happened. (can't say ive had the best start to the new year) any advice?