Scared to Miscarry. 3w6d pregnant

Hi! I’m 3 weeks and 6 days pregnant. According to my LMP my due date is 7/31/21. I don’t have any symptoms yet since I’m still so early, but I can’t help but feel worried that I might miscarry. I had a miscarriage in June. I went for my 1st prenatal exam at 7 weeks and heard a heartbeat and was told everything was fine! Then less than a week later I miscarried. I’m just so nervous. I wish my doctor can check my HGC levels but he won’t. 😫