Reality TV star and model Kendall Jenner has opened up about her experiences with anxiety, saying that she struggled with heart palpitations and couldn't breathe during such attacks."Two or three years ago I genuinely started having very, very bad panic attacks. I was having frights in the middle of my sleep, literally felt heart palpitations. I couldn't breathe. I was pretty bad," Kendall shared ahead of her four-part series with Vogue called "Open Minded", reports femalefirst.co.uk.She earlier shared that she has "struggled a bit" with her mental health.Kendall said: "I was really, really young and I remember not being able to -- feeling like I couldn't breathe and venting to my mom and being like, ‘Mom, I feel like I can't breathe. Something must be wrong'."She added: "She took me to a bunch of doctors just to make sure that I was okay physically, and I was. No one ever told me that I had anxiety. Maybe three or four years ago it came back completely full-on. I would have crazy panic attacks. I finally kind of got the information that I needed about it."Once Kendall knew what she was struggling with, she found new ways to cope.