Hi, I Hope You Can Help Me Please, I Wake

Hi, I hope you can help me please, I wake up almost every night shortly after I fall asleep, like 1/2 an hour after, abruptly, feeling as if I am dying, it feels awful, I am not sure what it is but it feels like something horrible is happening in my body, I can't tell if my heart is not beating, or if it is something in my brain, it feels very awful. It is not pain really but almost like not breathing; it it very "painful", meaning it feels horrible, I am now very scared of going to bed. It is physical, not mental.
Thank you