I have pain after ejaculation what could be in my age because i am young?

You did not provide sufficient information. Where is the pain, what is the nature of pain, how sever is it, how long does is last? Mild discomfort in the testes or groin is not a cause for concern. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.