Hello ! What you seem to be having is a panic attack. I understand that this can be very terrifying and you cab be absolutely petrified while experiencing the same. These usually last for sometime and then the attacks can be multiple in a day and hence you may develop a sense of impending doom.. We need to evaluate your mood , any stressors which you may be recently facing and also your thought process around this attack and what this means to you We may have to rule out medical conditions which may be contributing to it. You will benefit from Medications and therapy.