Leaky bladder after urination 21 year old male, problem started around age 15 no other issues and urine color is normal?

It's well past the time that you should have seen a Physician for examination. See your GP or a specialist Urologist.

If you're healthy otherwise, leaking urine after voiding is likely due to your poor habit. You should take time with each voiding, especially at the end and make you empty your bladder well with repeatedly contracting the pelvic floor muscles. Contracting these muscles is exactly same action when you intend to interrupt the stream during voiding. Milk your penis from base to the tip when done.