Like attracts like. Something about you or your environment, including people and energies around you resonated with it, allowed it to come into your sphere and for some reason you are on a similar enough wavelength that you can detect it. Very often this is not even about you at all, as these things are as numerous as insects in the real world, but we don’t normally sense them. Humans are deaf, dumb and blind to the astral for the vast majority of what exists.
In the same way that you go outside and don’t ask “why me?” when a fly whizzes by - flies exist and it’s not personal - it’s very likely that neither is this. This is the reason we cleanse ourselves and our spaces in processes that on this forum we term “having good spiritual hygiene”. You shower every day for the same reason - assume things you can’t see are in your space and all kinds of dirty and clean up so they don’t make you sick.
I see things from time to time, mark it as “that’s interesting why can I see it and why is it in my living room”, run a quick smudge, cleanse, ground and run the microcosmic orbit and wait before I draw any conclusions. But I’ve always seen “things” out of the corners of my eyes since I was little so to me it’s normal and always harmless. Like with spiders where you say “it’s more afraid of you than you are of it” - probably why it’s hissing it’s terrified, with good reason because humans are extremely aggressive especially when they’re scared.
Being a parasite has nothing to do with what it “looks” like.
Parasitism is not a type of being, it’s a behavior, meaning the thing is feeding on your energy. This is the definition of parasitism. Human narcissists and vampires are also types of parasites. If it’s not doing that then you have no problem. If it’s harming you then the only reason it’s doing that is to feed, like anything in nature these are stupid and instinctive, not malicious - humans are malicious not insects - so there’s no other reason really. Looking harmful is why people kill spiders which are actually beneficial - they are afraid for no real reason (outside rare cases and even then spider bites are defensive). Sweep it out like you would any insect.