Love Problem

There's someone in the world that I care about a lot. It's not their looks or their smarts, is who they are.
This person makes me feel so great inside when I'm with them.
But they don't know that every night I cry myself to sleep because of them.
The problem in this story is that, neither of them think that they are really happy.
Sometimes they ar totally in love showing off to the world, but then other times they don't want to see each other's face at all, and just flirt with someone else.
Is this love going dowhill? Should they break up? What should this couple do?
If they keep up with this, both will feel like crap and there will not be no changing back about how they feel, 'Cuz the person that you love doesn't change, love changes them.