No gestational sac yet at 4-5 weeks

Hi po mga momshies, possible po ba na too early pa at 4-5 weeks kaya wala pa makita gestational sac during ultrasound (twice). sa mga blood test including beta hcg positive naman na pregnant ako. I had bleeding kasi kaya worried ako as per OB threatened miscarriage pero tumigil naman. pero yun nga too early pa daw kya wala makita.