Does there is more bleeding during periods if i have sex on 3rd day of periods??? if so then what is the reason behind it??

Not applicable: Sex during healthy menstruation will not increase bleeding unless there is a reason for abnormal bleeding. 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. Wish you good health!