Hi I Am Currently In 12 Weeks Of Pregnancy. I

Hi
I am currently in 12 weeks of pregnancy. I am experiencing diarrahea sometimes with black stool (sometimes with lower abdominal discomforts) . Sometimes little blood with black stool. I am taking prenatal vitamins since pregnancy . Could it be the reason for black stool . Is it normal during pregnancy ? Or i should ask my gyn about this . I am worried