Can this be a ghost or just my imagination?

Ok so my grandfather dies last year and his 1 year anniversary is coming up this month. Lately, I've ben noticing a lot of activity in my room like footsteps and the computer chair squeaking. I always think it's my cat but when I look, I don't see anything and my cat is always on my sister's bed. My grandfather was very attached to me because I was his only grandson, so the only person that can carry on his name. He was also very sick mentally, so we never really had a chance to communicate but I could have felt a strong emotional connection to him. My parents always tell me that he's watching down on me, and I know he is but I mean I wake up sometimes and I'm scared shitless. I also have dreams sometimes where I see like white flashes in my room then I wake up sweating excessively. I can also feel an energy in my room sometimes when I'm by myself. I always have been afraid of the dark as a child but not this much...Any help or suggestions would be greatly appreciated.