Ever felt a deep sadness and not know why?

Today has been such a bad day for me emotionally. From the time I woke up I felt like I was drowning like I couldn’t breathe I had to take multiple deep breaths and I still felt like I didn’t have enough air. Throughout the day I felt such a heaviness in my chest it literally felt like my heart was hurting. And now the feeling of suffocating is back like I can’t get enough air. Idk what’s going on. Or why I feel like this. Is this normal? To have multiple I guess these are panic attacks? And not know what’s causing them because I was fine yesterday. But I’ve been off all day from the moment I woke up. It makes me scared to try to go to sleep when I feel like I can’t breath because I’m afraid I won’t wake up. Or that I’ll have a heart attack. Are these panic attacks that I’m experiencing today?