Chest pain and dizziness?

I'm 18, never smoked, rarely drink. But sometimes when I'm sitting or have just gotten up I'll get a pain in my chest, my heart will beat fast, and I'll get really lightheaded. Getting lightheaded after getting up is pretty normal for me, but I'm worried about the pain. Sometimes it feels like it goes all the way up from my sternum to the back of my throat. It's not indigestion or acid reflux. Any thoughts are welcome! Thanks :)