Simple as this - Look at your sentences. Are they all the same? I suggest you read your work, bit by bit, aloud. Listen to the rhythm. Is it monotonous? Poetic? Erratic? Momentum builds?
"This sentence has five words. Here are five more words. Five-word sentences are fine. But several together become monotonous. Listen to what is happening. The writing is getting boring. The sound of it drones. It’s like a stuck record. The ear demands some variety. Now listen. I vary the sentence length, and I create music. Music. The writing sings. It has a pleasant rhythm, a lilt, a harmony. I use short sentences. And I use sentences of medium length. And sometimes, when I am certain the reader is rested, I will engage him with a sentence of considerable length, a sentence that burns with energy and builds with all the impetus of a crescendo, the roll of the drums, the crash of the cymbals—sounds that say listen to this, it is important." Gary Provost (100 Ways to Improve Your Writing).
My suggestion then is this: Read a section aloud. Then go back in and vary length, tone, rhythms, paragraphs, white space. Read it again. How does that feel?