Ay sis, naiintindihan ko ang worry mo, very normal yan sa ganitong stage ng pregnancy! Actually, a few of my mum friends shared na ang FHR nila around that time ay medyo low din, and honestly, at 7 weeks the range can still be quite variable kaya hindi mo dapat mag-panic. The fact na may significant growth ang baby from your previous scan is really a good sign, so I think the one week follow-up your doc recommended is the right call, just try to stay calm until then (easier said than done, I know!). If your doctor isn't alarmed, that's actually reassuring, pero if you're still really anxious, you can always message your OB between appointments just to ease your mind. Rooting for you and baby, mama!