I moved to Macao about 1 year ago for work and I have been renting an old 2 bedroom flat by myself. A few weeks later I found a flatmate who sleeps in a bedroom next door. One morning my flatmate commented on screams and unintelligible spoken sounds coming from my room and asked if I had a bad dream. I had no recollection of any dream and I was aware that I sometimes speak out loud when I dream so I took no notice of it.
A few weeks later my flatmate made another comment about the noises, I thought nothing of it but then he told me it happens on a regular basis. I told him to wake me up next time, so I can recall what I was dreaming about.
It wasn't long when I had another night of noisy sleep, my flatmate came into my room and woke me up. When I was awake I was wet with cold sweat, and the bed mattress was hanging half off the bed. My flatmate told me I was moving violently in my sleep and we thought that's what caused the mattress to come off the bed. We turned on the lights to put the mattress back and noticed that there was a bit of water under the mattress. We lifted up the mattress and the wooden support beams that hold up the mattress were soaked. As if someone had poured a glass of water onto them.
My flatmate moved out of the house a few weeks later, and I have been living alone in the house since for about 6 months. I regularly lift up the mattress in the mornings to check it and the phenomena reoccurs on a regular basis. Each time it does I will leave the mattress off the bed, dry the bed and go to work. When I am back from work the bed is completely dry, however the water re-appears the next morning.
I have lived in Hong Kong and I have witnessed condensation appearing on walls etc on humid days but this is totally different to that. For one the water only and always appears under the mattress, and not on any other furniture. Also it occurs regardless of the weather and climate. I don't spend a lot of time in the house so I can't say I feel the house is haunted, also I have changed the locks since my old flatmate moved out so I can rule out anyone entering the house when I am not in.
What should I do, should I be worried or am I in any danger? My health is good in general, and I have no recollection of bad or good dreams. One friend who heard the story said it could be a water spirit/demon and warned me not to go swimming. I never learned to swim anyway so I don't go to pools or beaches.