Hi
It's very difficult to know everything from a very brief thread.
Usually, women Do have reasons why she's unhappy in their marriage and seemingly she is "acting out" to let her negative feelings out towards you.
Perhaps, she never expressed these /or something bothering her in an adult, civilized way to you.
It may not be your fault - it could be anything.
But it seems there are signs that she's very unhappy whatever reason(s) and she perhaps wants out (but she is unable to say this to you?) It is very sad when this happens but you cannot stay like this forever.
You have my deepest sympathies. You are not alone.