6 week scan-heart beat of 102bpm- help!

Hey everyone. I went in for my first u/s today at 6w0d. I had an IUI so they know exactly when I conceived. Baby looks great, but the heartbeat is slow at 102. They said its normal but want to check again in a week. Anybody with a similar heartbeat this early and everything was fine? I wasn't worried until they said they wanted me to come back. The baby measure at 5w6d so it's right on track. I need positive stories please!