7 weeks pregnant spotting for 5 days had ultrasound on day 3 of spotting, fetal heart rate 154, could this still be a sign of miscarriage?

Possible. While noting a viable (presence of fetal heart beat) intrauterine pregnancy is reassuring, a subsequent miscarriage is still possible. Risk of miscarriage depends on women's age, increasing with advancing maternal age. Important to note that bleeding during pregnancy is not uncommon. However, best to notify your ob-gyn if heavy bleeding and/or significant pelvic pain.
Yes, possible. Fetal heart motion is a very reassuring sign. The rate of 154 seems about right for 7 wks. Still, the risk of a miscarriage is about 15% rather than 5% if there were no bleeding or 30% before knowing about the heart motion. Stay positive, don't push yourself physically (mostly for psychological reasons) and get another check in about a week to confirm continued fetal growth. Good luck.