Hi there. You are definitely pregnant. However, the thing questioned here if the pregnancy is viable. At 6 weeks, a heartbeat should already be appreciated. There are two possibilities here.  1st, the embryo my not have  developed properly or,  it will still develop in a few days. You may repeat your ultrasound about 1-2 weeks from the 1st ultrasound was done. Feel free to ask if you still have additional clarifications. ... 
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