Ultrasound at almost 6 weeks??

I had a transvaginal ultrasound on what we thought was 5 week 6 days . Only saw yolk sac and gestational sac . No fetal pole or heart beat. Doc says It could still just be too early to see baby. I have been having a lot of consistent mild cramping for the past few days with no bleeding at all . Next ultrasound is in 2 1/2 weeks ... I know its way early to have an ultrasound but has anyone else experienced this and baby ended up showing up later on and being totally fine ???

UPDATE - thanks so much ladies... I had another ultrasound at 8w5d and saw baby and heard the heartbeat ! Everything looks really good!!