Hi Got My Tvs Ultra Sound Done And It Was

Hi got my tvs ultra sound done and it was 8.5mm with my hgc 5500..i had done my tvs ultra sound 10days back and the yock sac was 4mm wit no hearth beat no featus visible as if now..my doc says the growth is slow nf if it dows not increase then we hav to terminate the preg..i am scared i belive im just 4 to 5 weeks pregnant..is this normal or ok.pls suggest as i m very sacred