Does a heart attack feel like something stabbing you in your heart into your back?

It can: Heart attack can have severe retrosternal pain which may radiate to shoulder, left arm, jaw, also to the back.

It may: It may feel like that, or these may be the symptoms of a dissecting aneurysm. Or, it may be something entirely different like acid reflux or a pulled muscle. Go get yourself checked right away, especially if this is the first time you are having these symptoms.