Need Help

So I have been a little conflicted between reminding my boss again or not. I work in a warehouse so I do alot of heavy lifting (which I have been avoiding the best I can) and alot of walking around in a place where it easily 90degrees+ everyday. I told my manager 3 weeks ago if I could get switched somewhere I dont lift boxes. He said he needed a doctors note which i gave him but still nothing. What should i do ? Btw im only 7weeks so i really dont want to risk anything.