First prenatal visit!! Need answers !

Had a sonogram yesterday seen sack with yolk sac but no fetal pole . My beta levels are 29,601 and they show me measuring at 5 weeks 2 days . I thought that with levels that high that I should have seen a fetal pole ??????? I should be 6 weeks today . Doctor gave me a paper when I left stating that I was having a threathen miscarriage ???? Why my levels are high , sac is present , yolk was present ? I’m so confused . I have had 3 living babies so this isn’t my first rodeo! I’m scared and stressed out .