JUST A BIT WORRIED....

hi everyone i decided to join this forum cause something is really freaking me out. well lemme explain. im at my study desk on my computer and i see the curtains blowing. ok so the first thing that comes to mind is to close the window. i do that , then get a quick drink / toilet break from homework. and what do you know the windows open again.... i didnt even realise it was open till at night it was very chilly. also when i go to sleep i hear creaking noises on the ground in the house. in the kitchen mostly. our house is wooden flooring and is constructed in planks andd is about 60 years old now. when you walk or sneak around it creaks which is normal. BUT NOT AT NIGHT WHEN NO ONE IS AWAKE!!!! pls someone help me im freaked out.. currently typing this i feel someone is behind me which also makes me nervous ... thnx for listening guys. help would be apprecaited.