Spotting

My last menstruation was June 20 and had a PT after July 20 and its positive. I went to OB and I was advised to come back for an ultrasound by week 7. I experience a very very slighy spotting in Week 6 that didn't last for a day but I got worried and had a check up with a different doctor and was advised that spotting is normal as long as its not a heavy bleeding. The doctor provided me supplements that will last for a month and told me to have an ultrasound by week 10. I had another slight spotting last wednesday and it did not last for an hour, none for thursday and a little bit on friday. I'm not sure what to do next, do I have to wait for another two weeks to get an ultrasound? I hope my baby is fine.