Am I pregnant? D:

So I usually have pretty heavy periods lasting about a week. And I started my period and I've had all of the usual period symptoms, and everything was normal at first, day two heavy, but day three and four (today) there wasn't a lot of blood... there was definately some but not I'm talking an end of your period amount of blood. It is not normal for me period to be light or end early. I'm on day four and there's still some blood. But my boyfriend and I looked it up and it said I could be pregnant and I'm terrified, I'm too young to be pregnant :( help!! (Btw, unprotected sex but he pulls out, ik I'm stupid I need birth control)