This is surely an entity. It feeds off of your energy and becoming stronger. My advice is to ask your Spirit Guides to help getting rid of the entity and also, perform a cleansing ritual for yourself and the house. Furthermore, you may use special crystals that help for cleansing, banishing and protection.
Lastly, I suggest to raise your vibrations, because when you have low vibrations you attract entities with negative vibrations also. However this isn't going to be done in one night... Your vibrations may not necessarily be that low, but the entity may influence you with negative emotions and all these symptoms, and that may make them lower.