Please read what I wrote, I didn't see it....my brother, as a child did, now his first born son is seeing it.
I was speaking in the generic. Assume I continue to do so.
“In the land of the nails, every monster looks like a hammer.”
For most people, there is a problem of trying to force what they observe that is unknown, into the very restricted template of what is known to them.
For instance, if you had never heard of a polar bear, when you saw one in the wild, would you think it a demon, or an angel? If you guessed that it was an angel, because it was white, and thus was friendly, it could get you in a lot of trouble. However, while it would be safer in that case to assume it was a demon, there is still no pressing need to destroy it because you assume it is evil. It is neither. It is a bear, doing bear things as God intended. Leave it be.
So, as has been suggested by other posters, since what it truly is, is unknown (though what it is assumed to be is a demon), instead of assuming it is a demon, assume that it is an unknown, and seek guidance of someone who might know what it is. Do not rely on your own judgment, find an expert.
Importantly, if you approach an expert and say that you are being menaced by a demon, like most people they will be dubious, even if their expertise is in demons. But if you approach them and say that you do not know what it is, but suspect that it is a demon, and need their expertise, they will be far more inclined to investigate.
And you both need and want them to investigate. That is the bottom line.