I Don't Know What To Do Anymore Because I'm Constantly

I don't know what to do anymore because I'm constantly tired, but when it's time to go to bed my body won't let me. But when I do fall asleep my heart will start beating really hard and fast then I start shaking. My mind will tell myself to wake up but I never do. I always end up screaming and then waking up. It's horrible. All I want is sleep... it's been happening for the past year, I keep thinking it will go away but it's not. I'm also just 16... any suggestions... I really could use the help.