You need to learn a banishing. Even if you think it’s getting in your way, you need to push through and learn it, and start using it every day.
Banishing is the foundation of magick, you’re gonna have to learn it.
Another thing to keep in mind - this imposter is not in you. It does not have any power, the only thing it can do is slightly nudge your thoughts like a little parasite.
So keep calm, and realize it is impossible for such a thing to do anything. It cannot harm you, it cannot manipulate you, it cannot cloud your judgement or connection to a spirit. You are clouding your connection because of the doubt you believe is the spirit.
A few good banishings and it will disappear for good (if not right away). If not, it is very likely you are the one at fault - ie tripping over yourself by believing it is a spirit, when you are doing it to yourself. It is very common in new magickians. Keep banishing and work on getting your mindset straight.
Moreover, I suggest you workout. Working out is a must for every magickian. Resets, balances, integrates and grounds your energies, and allows you to develop much quicker. As above so below holds extremely true. Everything is spiritual, everything is physical, there is no distinction.
Don’t listen to the likes of SatansWife, who does not even practice.
Another thing, don’t start calling up spirits and giving them things until you fix this. You’ll just overload yourself. Fix yourself first.
Banish, workout, repair your mindset.
Few weeks if you follow my advice and you’ll be a golden egg.