Is prostate examination or dre bad for health? the dr did it rigorously that makes precum out in 15s.will it cause prostate congestion or prostatitis?

No risk, no worry: It is normal to express fluid with a vigorous prostate exam. Digital rectal examination of the prostate is harmless and will not cause either "congestion" or prostatitis. However, this is an unusal examination for a 16 year-old unless there was already evidence of a prostate or urinary infection. If you have prostatitis in the future, it will be from the underlying problem, not the examination.