It sounds like all is well. I sometimes can't find a heartrate until after 13 weeks with my doppler, despite doing some searching at earlier dates. Maybe it's an anatomical reason, sometimes if there's a little extra "padding" in that area, or the placenta might be right in the anterior, blocking the heart rate until the baby gets higher. And the fact that you saw a great active baby - that's a wonderful sign. I would say -- RELAX and ENJOY!