Worried about baby

Its my first pregnancy. Currently 6w5d on app however, I went for a scan last week when I'm 5w4d, gynae say too small can't see ultrasound and transvagina ultrasound. Ask to visit the hospital with a more detailed scan, was told that AUA is actually 6w2d instead. However, dr say no heartbeat detected. Advice to do blood test to test HCG level. Hcg level is 4k to 9k, not too much of a increase, did another ultrasound, still can't see. Any case that its just too early or it's a sign of miscarriage? No tummy pain, no bleeding. Still have pregnancy symptoms like tender breast, fatigue and high body temperature. Update: went to the gynae 1 week later and we manage to hear the baby's heartbeat ! And dr side shows that I'm 6 week 3 days, Previously was too early to detect the baby and the heartbeat.