Gore gap

[taxmapper]

so those uninitiated, the center panel of a bra is called the "Gore". (Yeah kinda Star Trekkie here), but the gore in a typical bra is "suppose" to sit flat.  

Today with a 2 year old bra I am getting a 1/2 gore gap.  Meaning they are now starting to exceed the original intent, but its also a milepost of a datapoint showing they are continually growing. 

[Parity]

  Your right in that it should rest on and make full contact with your body.  Not enough room in the cups for the breast tissue will what you described.  Also you mentioned the age of your bra.  As they age they relax and loose their ability to fit properly and can be some of the issue.   It has lived a nice long life and is in need of retirement.  Sounds like bra shopping is in your future.