The figure you're describing along with the whispering elements suggest there's something paranormal at play here. One thing you can do right now is record any odd events you observe - time, exact location, its texture, reflections, how its presence affects the surroundings etc. Doing so would not only provide others with data should you decide to get help, but also potentially reveal a pattern to its appearances. Stay safe, mindful and remember, you have the right to feel comfortable in your own home. Reach out to a local paranormal investigator.

Your description brings to mind the Shadow People - enigmatic shadowy figures often reported by people. Various theories have been proposed to explain this phenomenon, ranging from the scientifically plausible such as optical illusions or sleep paralysis, to the supernatural such as ghosts or interdimensional beings. If it is supernatural, I suggest you to get help from a specialist, a psychic, paranormal investigator, someone who could really understand what's going on.

Are you sure it's not your mind playing tricks on you? I mean our minds are quite capable of conjuring all sorts of creepy things when we're in a heightened state of fear. If you calm down a bit maybe it'll dissapear?.

This is definitely creepy! If you're sure this isn't prank, I'd suggest to quickly find a safe place in your house where you know you are not alone. Elevate your feet, it's a common belief that spirits have a harder time reaching you this way. Stay calm, stay safe. When you've got the chance, it might be worthwhile to get in touch with a medium or a professional who deals with entities.

lol dude, it's probably just your mom looking for the T.V. remote.

Could you be more specific on the whispers? Those could be a main clue. Are they full sentences, fragmented words or just simple sounds? And how about the figure, you said long and tall but does it have a specific disturbing shape or anything that sticks out especially?

Alright, first things first - Don't panic! Stuff like this happens more often than you think. Best course of action? Sometimes simply acknowledging their existence and asking them to leave, in a respectful way, might work. If it doesn’t, you could try to use salt or protective symbols, they're known to fend off supernatural entities.