My 18 month old son is having (what I believe to be) night terrors. Wakes up in the morning and from naps in complete hysterics. He thrashes in his bed, screams like he's being hurt and nothing will soothe him for at least 20 minutes. He doesn't want to be held but doesn't want to be put down. Doesn't want a snack. If I bring him outside to play, he just screams outside. I've even tried a tv show/movie. I have also let him cry it out in his bed, which only made it worse. Anything else to help him?