recently i have been getting headaches and feel out of breath even when im not doing anything like i could just be laying in bed and it'll feel like ive just ran 5 miles and just as quickly as it comes it goes away. usally right after that my heart will start racing and ill feel an uncomftorable tightness in my chest.sometimes itll just get really hot even if the AC is on. i have a history of anxiety but ive never felt like this before. Is it just anxiety or is there something more serious going on?