I had sex once and three days later i got a light brown period for about 4 days. we used a condom but i am still nervous that this light period bad.

Light period: The main reason for light periods is a change in hormone levels. Causes for what seems to be a light period can include: thyroid problems, eating disorders, excessive exercise, initial periods for a girl, use of an intrauterine device, oral contraceptives, perimenopause & implantation bleeding in early pregnancy which rarely occurs.