I suffered from a concussion 6 weeks ago but still feel a little foggy. is it alright to resume weight training?

Check with your doc: Usually after a minor concussion (i.e. no real loss of consciousness or if so, briefly) most people your age can bounce back to normal activities inside of a week. However, if you've been off for 6 weeks that suggests to me that your incident may have been more serious. Therefore, I suggest you check in with your doctor to get a clearance before returning to activities that could be risky.

Yes, but: Work into it a bit slowly. You might find that bearing down when lifting causes headache for a time.

Concussion : No. Lifting weights will increase pressure in the brain. Until the fogginess resolves it is best to rest. See a concussion expert and consider an MRI of the brain to check for injury related to the concussion. Neuropsychological testing may be required also to identify any cognitive damage and to start exercises to improve thinking.