gestational sac 5weeks5days crl cannot measure because its small

i had my fisrt check up to confirm my pregnancy and i dont remember my lmp then they see the gestational sac and a heartbeat but it was so small thats why they cannot measure the crl so my doctor said to come back after 2 weeks. i am worrying because my first pregnancy happen to be mmc 7weeks4days no heartbeat at all..and after my dnc a month a go i was again pregnant and now she is 1year old and 3 months i want to gave her little brother or sister for the last time.because i am 41 years old right now thats why we are trying another 1 until nxt year may but i never thought that i will be pregnant with 1 attemp only. do i have to worry about this??