Can't sleep : rapid heartbeat and breathing and dizziness?

At night when i'm about to sleep my heartbeat and breathing rate accelerate suddenly and i feel so dizzy that it wakes me up. I think those symptoms are pretty recent. Though i must admit that i have a bad tendency of sleeping very late and it takes a long time before i fall asleep. It seems like I rarely sleep deeply and i usually wake up in the middle of my sleep. When i'm asleep i usually have bad depressing dreams (not always nightmare but still depressing) and my morning seems also very gloomy because of this. Do i suffer any serious illness?