Worried Mama 😔

So I got a ultrasound yesterday and I thought I was 7weeks + 2 due to the fact that I used a ovulation kit to track for baby making time. Baby was measuring at 6 weeks. I didn't get to hear a heart beat but got to see flutters. I got my blood taken today and my levels are 5000. Still within the 6 weeks range but, on the low side. I'm not bleeding but, having lots of cramps...but I've had those since the day I found out I was pregnant and I also chase a 2 and 3 years old around all day. I have a follow up u/s next week. Should I be worried ?