I have sternum pain right below my right breast, i get the diagnose from clinic, idk the reason i got this, does wrong sleeping position / excessive masturbation cause the pain? what dos & dont having sternum pain?

It is not feasible to provide a meaningful opinion without examining you. One thing I can assure you of is that it is not due to masturbation. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. For nutrition: http://www.choosemyplate.gov/. Get HPV and Covid vaccines.