I'm not saying that it's not possible, but the first thing that you should do is maybe go see your doctor for a check up - just to rule out the possibility that you are having auditory or visual hallucinations. There are medical conditions that could cause such things, and it's always better to rule out any mundane explanations before turning to the supernatural.
Otherwise, there are many anecdotal stories of people's encounters with ghosts, so who's to say that it's not possible. I don't think it's really considered "normal" to see them, but I wouldn't necessary call it "abnormal" either.
The 1st answer was good advice but I would like to add that if you are not having a medical problem, be careful of the sprit you see. Most are not good sprites. I do not think you are see ghost of actual people, but of something else. God said he was not a God of fear. I would suggest that you get a bible and read it. Start in New Testament. I think they will go away while you are reading.
Apparently it isn't normal, but I only found that out after talking to others about it. I can sense them and on occasion see and hear them. My daughter can do all three. I've dealt with it for so long that it seemed normal for me and it kinda fried my brain that not everyone experienced such things. I would watch those ghost shows and read stories online where people would be afraid because something moved by itself or an unseen hand touched them, or they saw a ghost walking down their hall and I'd think, so what, doesn't everyone experience that?? LOL apparently they do not. But just because others don't, doesn't mean that you are crazy or anything because it DOES happen to some and do not ever let someone tell you that you are crazy or lying just because it's never happened to them.