I Am 15 Years Old, Female. About A Week Or

I am 15 years old, female. About a week or so ago I started getting these random 'attacks'. When these attacks happen I feel my chest become tight and my limbs as well. I get the feeling of being very hot and my knees become very weak as well making it difficult to walk. I also find it hard to breathe. These usually last about 10-30 seconds and so far have been happening around 2-7 times a day. I have past diagnoses (chronic depression and anxiety disorder) but recently have been cleared as fine by a doctor as my anxiety and depression have gotten far better in the past year. These sudden 'attacks ' feel differently than any anxiety attacks in the past so I am unsure about their cause.