Sayang, don't worry lah, you're not alone with this! At 7 weeks, it's actually quite normal untuk nampak kantung je first, especially kalau timing of ovulation was a bit later atau exact dates are unclear. A few of my mum friends had the same experience, and then a week or two later the baby showed up perfectly fine with a strong heartbeat
The good news is your doctor already detected the heartbeat, which is a really positive sign! Usually by 6-7 weeks the fetal pole and heartbeat should be visible, so having that degupan already is encouraging. Most doctors will ask you to come back for a follow-up scan in 1-2 weeks just to confirm everything's progressing beautifully, it's standard practice, not something to stress about.
First-time mum jitters are legit, but from what I've heard, cases like yours usually turn out perfectly fine. Just take it one scan at a time, and do check in with your own doctor about the next appointment schedule, they'll give you the clearest picture of what to expect next!