So nervous for first US on Thursday

This is my second pregnancy and so far has been completely different from when I was pregnant with my daughter. With her, my levels were rising so quickly and fast they warned me I may be having twins, I was nauseas all the time, and just overall felt "pregnant." This time, I don't feel sick at all, I just have occasional tenderness in boobs and really bad exhaustion, chills, and some
random side twitches here and there. I have gotten so nervous over this pregnancy I went to the ER twice to get my levels checked (I just moved so I'm a new patient so my OB won't see me till 8 weeks). My first level was 3500 and a week later it was 13, 794. The nurse practitioner said I had nothing to worry about but I can't help but worry that my levels didn't double. I feel like I'm walking into Thursday's appointment knowing this pregnancy is not viable. I'm feeling down about the whole thing and would love some encouragement from other people's experience.