7 weeks! Wow this pregnancy is going fast! Buying a doppler was the best thing I ever did. I can't remember where I got it from but I only ended up paying around $50 plus postage so make sure you shop around - you can get seriously ripped off otherwise!! Just don't be alarmed if you can't hear it at 12 weeks....its quite common not to be able to hear it until around maybe the 16 week mark.
Has morning sickness kicked in yet?