Have you had an ultrasound lately. I tend to bleed during my pregnancies but it is only a small amount. Did they say the position of your placenta? Sometimes if it close or covering your cervix that can cause you to bleed. I would let your doctor know .
keep any eye on it, bleeding in pregnacy can be common but it is not considered normal, it can be caused by a number of things, after sex, irritable cervix etc, if you start to experience any cramping or it looks like its getting heavier, you should get checked out asap, otherwise it if seems to have settled just make sure you mention it at your next appointment