I think, after a while of writing one form of fiction, most of us probably feel stale, run out of ideas and steam, become formulaic or simply get bored.
It's normal, it's understandable, but don't let it get you down. You're still a writer. The answer is, try writing something else for a while. Something not aimed at the womags. Enter a competition, try some poetry, write something for your blog, start a novel, try NaNoWriMo, or just write whatever comes into your head even if it is nonsense. No writing is ever wasted, in the way that no physical exercise is ever wasted. You're practising, building up muscles and gaining experience. It's worked for me, with the historical novel.
Emma Darwin has written a brilliant blog post on this - you can read it here.