Please help! Weird feeling in my heart, it aches and feels like it's being pinched?

I don't think it's heartburn. I've rarely ever had heartburn and the only times as a kid when I ate too fast. With heart burn, I remember it hurt to breathe in and actually did feel like a burning sensation. This is different though, doesn't hurt more to breathe in. First noticed this about a month ago. I was lying down and my heart felt...cold and wet? It was so mild but was bugging the heck out of me, it was gone by morning. Now, about a week ago it came back, and has been progressively getting worse with each day. First, it was a cold sensation, now it's an achy one. Like I have cramps in my heart. And at random times I will feel a huge pinch in there. It's not small, feels like my whole heart got squeezed or kicked. My heart feels like it's heavy when the pinch happens. I felt one of these 5 minutes ago and have been all day. At one instance, I twisted my torso to help with the achy feeling, and my shoulder then began to ache and then my elbow. I'm scared, I'm 18 and this has never happened before, so I don't understand why something would be wrong all of a sudden. My eating habits haven't changed, nothing has changed. At first it was only happening in the evening, but I woke up today with it. I wondered if it was linked to eating, so I skipped breakfast, still the sensations were there. It hurts now it aches pretty bad.