Should I retake?

Hey guys. I took the SAT in January and got a 1510 (770 Math, 740 Reading and Writing, 17 Essay). I took it again in March and just got my score back. I got a 1500… the only thing that changed was that my Math score went down by 10, and my essay went to an 18. Is it worth retaking, considering that I am aiming for very selective schools such as Michigan, Notre Dame, Northwestern, and UVA? Both times I took the test I got a 35 for Reading and a 39 for writing. I know that the reading score is pretty low… do adcoms see the individual reading and writing scores, or do they only see the 740 total? If they can see my 35, should I be retaking to raise that? Also, is my essay low enough to warrant a retake? Is there really much of a difference between a 1510 and a 1550-1560, or should I just be happy with what I have and move on?