Hello, yes you can do weight lifting as you are doing before. But for this you have to sure that your forarm X-ray shows complete union of the fracture
, you are able to do all the movements of your left forarm as your right forarm(you can take help of physiotherpy) and do as much weight lifting which will not cause u pain in left arm (not try to compare left arm with right arm, left arm can take 1-2 more months to recover, it will depend from person to person). If you are taking proper diet and doing regular movement exercise of forarm if your X-ray and orthopeadics says that your fracture is completely united than start increasing weight gradually (make sure you are not in pain). You will surly recover in few days or months. Have a healthy recovery.