I was suppose to have my period but when i would change my tampon it would be brown not red and it was for four days straight what is it?

Old blood: Brown blood is just old blood. It's okay and isn't a sign that something is wrong with your body. Sometimes as we age, the color of our period can change. Less red and more brown. If you are having unprotected intercourse, sometimes it can be a sign of pregnancy, so if that's a chance, you may want to take a pregnancy test. Hope that helps!