Feeling sick. :(

So, this has happened alot here lately and I'm worried. My heart starts racing, I start shaking, I feel like I'm going to pass out, I just feel awful. I think I might have high blood pressure, but I don't know what's causing it. I never see my doctor enough to tell him and if I call they always say the closest appointment they have is in 3 weeks, like two days before my already scheduled appointment. I feel really hot but my skin is ice cold. What in the world is wrong with me?