Throwaway account for soon-to-be obvious reasons.

I'm at a loss of what to do about my situation and it's complicated, so please be aware a wall of text is to follow. I'll try to be concise.

My wife and I have been married for five years. We were both healthy and happy people despite some trauma in our past. (Her parents died in a house fire when she was a teen. I did not have a good relationship with my parents and so I lived with my older brother most of my life.) We both went through therapy years ago to deal with these issues and there are no drinking, drug, or mental health problems for either of us.

A little over six months ago we moved to a house in Louisiana after I got a new job. This was our first home purchase, and although it was a very old home and needed a lot of fixing up, we were excited. About a month after we moved in, my wife began complaining of nightmares. It was so bad at one point that she did not want to fall asleep. In a completely random occurrence, we ended up running into a person who was related to the former owner of our house. She told us a bit of history about the house. According to her, our house was "haunted" and the former owner (an elderly man who passed away) complained about it regularly, but was too old and stubborn to move. Neither my wife and I are religious or spiritual, so we laughed it off.

After this meeting, my wife's behavior slightly changed. She was a little more distant and I kept catching her talking to herself. Her nightmares weren't as frequent, but she was acting super weird. I would wake up in the middle of the night to find her standing by the side of the bed looking at the wall, or staring out the window into the dark. She didn't act like she was asleep or anything, because I'd ask her what she was doing and she'd tell me she was just thinking. Around that time, I came home from work and she had been painting a bedroom. We hadn't moved anything into the room yet, because we knew we wanted to paint it. As I was walking down the hall to the room, I could hear her talking to what I thought was herself. Her voice was muffled through the door, but I definitely made out a deep male voice respond to her. The hair on the back of my neck stood up and as I reached for the doorknob I distinctly heard the male voice say, "He's coming." At that point I whipped open the door. There was my wife, in a completely empty room other than drop cloths, staring at me and annoyed. There was nobody else in there and nowhere to hide. It freaked me out and I told her to tell me who she was talking to. She appeared to be pissed off and just said "nobody" and went back to painting. She refuses to talk about any of her strange behavior.

There have been multiple other things that are happening around the house that I can't explain. There was one incident that especially terrified me and was unexplainable, but I still don't believe in ghosts or anything. At least, I don't think I do. Now, it's becoming a little more difficult. For every weird thing that seems to happen, my wife starts acting a little stranger. I bought a carbon monoxide detector thinking that maybe there's CO that affecting both of us (and it being an old home). I also got the house checked for radon which was clear too.

I don't know where to turn. We're not religious, she has no family, and I have an older brother whom I am not really close to. If I tell this to a therapist they'll think I'm crazy. I'm not sure what to do and now I'm creeped out by my wife and the house.

TLDR: Since moving into an old home, my wife has been acting strangely and unexplainable things are happening that are scaring me.  I don't know who to turn to for help.