I was due to get my period on the second. Today is the seventh and I started getting extremely bad cramps and I felt myself get my period so I went to use the restroom and I had stained my underwear. When I sat on the toilet, tons of blood came out. I am continuing to have cramps were I had to take medicine for it. It seems like I'm only bleeding when I sit on the toilet and it's a lot of bright red blood. Please help me figure out if this is implantation bleeding or my period. I'm 16 and cannot be pregnant.