Ghost/spirit in my home?

Hey everyone! I, 22 F, live in my great grandmothers old home. I sleep in her old bedroom.
I have been waking up every night to my door creaking opening and closing. (my door does not open and close without human force. there is a literal brick stopping the door from shutting). I also see shadows sprinting across the corner of my eyes constantly throughout the day in the daylight.
I did not believe in this stuff until now.
Last night I woke up to my door creaking open, and my cat laying next to me, looking at my doorway in absolute fear with his ears back for about an hour. His gaze looked around my room as if he was watching something slowly walk around my bed.
This only happens when my boyfriend is not in bed with me, or dead asleep. This happens about 3x a week. I am exhausted and losing sleep. I say a prayer out loud and it does not work. I am so scared, and so tired. I refuse to use an Ouija board etc.
please help.