Worried?

 So I usually take a cheap test about every week until my first appt.
So I decided to take one this morning and it started to show up but it's not as dark as my previous test have been!
I'm freaking out because of it! I know it could be because I didn't use as much urine or something  ( or I could be just making up excuses)   But this has me worried and wonder if any other ladies have had this happen? 
The top test is from April 7 and the bottom is from this morning.
 I'm currently 7wks 4days.