Hey Hun,
I was the same & knowing my history my GP referred me to get an u/s at 8 weeks under the description of unsure dates, why don't you ask your GP, at least seeing the heartbeat would ease your anxiety a little.
I still worry every day on & off, not much I can say to help you feel better but try to trust your body, it can nurture your little one.
Praying for a happy healthy full term preg for you xo