I'm 5 weeks pregnant. i had in early vaginal ultrasound because of very light spotting. the sonographer saw what appeared to be a sac but could not see the yolk. she also saw some blood inside my uterus.i haven't had any bleeding since. what is it?

Early pregnancy: In very early pregnancy you may see a gestational sac (GS) but not the yolk sac. The yolk sac may first become visible at 5 weeks with a GS diameter (GSD) of 5 mm. However, it may not be visible until a GSD of 8 mm. The blood is a subchorionic bleed. It confers an increase risk of miscarriage. You should do a follow up sonogram in 1-2 weeks to confirm pregnancy viability.