Spotting while 6 weeks pregnant

Last thursday I went to the dr thinking I was having a miscarriage because I was spotting when I wiped there was red with some stringy stuff I told my dr that they did an ultrasound and they said the baby was fine and still in the uterus where it should but here I am a week later still spotting is this normal?

(I have been having mild to sharp cramps and lower back pain)