What is this feeling in my chest?

Though never officially diagnosed, I have suffered with depression all my life. Sometimes it's fine and I can "ignore" it, but at others, I tend to feel 'ending things'. At moments when I am sad, I tend to have a feeling in my chest almost like how it feels in your stomach when you go down a steep hill. Weird way to put it but c'est la vie. Does anyone know what this feeling is? I was reading about Broken Heart syndrome, and was wondering if it could be the weakening of my heart from severe depression and sadness.