Bleeding while pregnant?

So I’m 4 weeks pregnant and I started bleeding really bad and I’ve been cramping a lot recently but I don’t know what’s going on.... I’ve asked family members about it and they said it was a possible miscarriage or my body was just getting used to the baby.... I’m going to the doctor later today but I wanted to know what everyone else thought it was... mind you I am a teenaged girl who isn’t completely grown so I can understand if I am miscarrying but it’s still sad obviously... somebody please just let me know what’s going on