My ultrasound said i'm due 7-14-14but my period was light & short only 3days is that my implantation bleeding or my real period had sex 3, 4, 8, 12, 15, 21?

Light Bleeding: Rest assured that in the early weeks of pregnancy, a little spotting or bleeding is very common. The most common cause for experiencing a brown discharge during pregnancy, especially in the later half of the first trimester, is that the body is getting rid of the older blood remnants in the cervix. As the baby grows, the original blood which is used to protect the womb is no longer required.