Oh, I see. It is possible you could be 3 weeks pregnant I suppose if a blood test is what confirmed it.
Oh hun, I feel so bad for you. Cramping I think would be fine, people often feel crampy like their period is right around the corner. But bleeding is not okay.
What color is the blood?
I wouldn't take any chances, I'd call my doctor right away. Sometimes when you find out really early that you're pregnant, these things happen

I'm so very very sorry.
Remember that nearly half of pregnancies are thought to result in a miscarriage and most people never even knew they were pregnant because it happens so very early, and it seems just like a normal period.
I wish you the absolute best, and please update after you've spoken with your doctor!