Dream of girlfriend, hands

I had a dream last night where i was laying in my bed and there was someone in all black holding me down and i could feel their hands on me where they were holding in my dream. i was calling out to my girlfriend for help but she just stood there and didn't move. it was really hard for me to wake up and every time i tried it was like whatever it was holding me wouldn't let me wake up, what does this dream mean?