Over the last couple years I started having anxiety attacks. But only when my stress gets extreme.…

Over the last couple years I started having anxiety attacks. But only when my stress gets extreme. Sometimes i won't even realize how stressed I am until I have an anxiety attack. And I have felt so emotionally unstable lately. As if something is building up inside my chest just waiting for the next little thing to set me off. Has anyone else felt this way? It's like I just want to cry as if someone has died for no reason. But I dont. I keep calm because that one thing, whatever it is, hasn't set me off yet. The anticipation is horrible.