Tests getting lighter? Should I be worried?

Mandy • 29 years old - Married October 2013 - Mom of Baby Girl Dec 2015 😊 Expecting Baby Boy April 2018 ☺️
Details: I'm 4+2; waiting on ObGYN to call back so I can schedule my blood test and first prenatal. Just worried. 
Top - yesterday morning; middle - this morning; bottom - 3 hours later

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