Chest pain, and im 13 weeks pregnant!!!?

I have been having pain in my chest the last two days off and on. The pain is sharp, then turns to dull and achey. I get really tired, and faint after the sharp pain, and want to lye down. Its not so aweful to take myself to the ER, But it hurts to bring me to tears. I just want to know what is going on. I know what heartburn is, I have it already, and its more centered to my chest, when I get heartburn. But this pain is to my left side under my breast. Im worried about the baby. A few years ago I was diagnosed with an enlarged heart, but never went for further testing. I just need to know what to do, and what is probably going on!!!