What Causes Loss Of Consciousness,breathlessness And Heaviness In Chest?

Hello,I had somewhat of a scary moment. Me and my boyfriend were taking a shower together. And I think I blacked out. I remember my legs feel really weak. And saying I couldnt breathe. It felt heavy on my chest. I woke up to him carrying me into the room. I don t know what happened in between but I was shaking from my hands to my legs and felt very scared after.