Pregnancy nightmares?

Ok..I've had vivid dreams throughout my pregnancy so far (I'm 18 wk, 5 days) but never nightmares until last night...I don't know where it comes from. The dream was basically about werewolves. I was asleep (in the dream) and I thought I heard one of my nieces crying and so I jolted awake and then realized I was at my house and they weren't so there's no way they were crying. I fell back asleep and then immediately dreamed. It started out that I was in a crowded subway trying to save everyone there because someone was going to release demons into the subway. (Because it was a big crowd) and then I went into this back room and ate with my niece and husband. And then we went to some other place with a few people and something about the other people set me off. Like.. I think I fell asleep at the other place and the rid niece.. and I woke up in that place scared and tried to make something to kill them but it made them mad and I woke up as one was trying to grab my neck.. it sounds dumb but it's completely shaken me to my I don't want to move and go to work because I am so scared now. I want to call my sister at 530 am to have her let me talk to my niece... it's so weird. Does anyone have any experience with this?..any tips?..