**Reason why I see people in my room at night?**?

Basically, nearly every night I will wake at around 2ish in the morning and see someone in my room. Not just like in a dream either, I mean I will PHYSICALLY see and person, there real, I can sense it. They never really move. Sometimes its a person I don't know. A few times I've seen myself, looking at me. I've seen my dad staring out the window though he swears he never comes in when Im asleep. I've seen my best friend sitting on my bed. An old man standing next to me. Loads more. Its starting to scare me. It frightens me so much I force myself to look away and hope they go. They normally do after a few minuets. I don't know what these mean or why I have them but its starting to creep me out. Could this be a medical problem or something else?