Like you have mentioned in the label to this question, your symptoms do sound very much like an Anxiety disorder.
Anxiety, when experienced beyond a threshold, produces myriad physical symptoms like chest discomfort, headaches, palpitations, sweating, giddiness, a feeling of impending doom, and so on.
The important fact about anxiety is that although it might seem difficult to pin point a reason for what causes it, finding it out it essential to weed out the problem from it's core. Therefore, apart from the lifestyle changes (healthy diet, exercise, deep breathing, etc), you need to get to the root of the problem. For that, you need to consult with a Psychiatric professional, in person, who can discuss your problems in detail, and devise a management strategy unique to you, and can include counseling, relaxation exrecises, mindfulness mediatation, to anti anxiety medication.
Seek professional help, in person. Good Luck!
While most people with anxiety disorders need psychotherapy or medications to get anxiety under control, lifestyle changes also can make a difference. Here's what you can do:
Keep physically active. Develop a routine so that you're physically active most days of the week. Exercise is a powerful stress reducer. It may improve your mood and help you stay healthy. Start out slowly and gradually increase the amount and intensity of your activities.
Avoid alcohol and other sedatives. These substances can worsen anxiety.
Quit smoking and cut back or quit drinking coffee. Both nicotine and caffeine can worsen anxiety.
Use relaxation techniques. Visualization techniques, meditation and yoga are examples of relaxation techniques that can ease anxiety.
Make sleep a priority. Do what you can to make sure you're getting enough sleep to feel rested. If you aren't sleeping well, see your doctor.
Eat healthy. Healthy eating — such as focusing on vegetables, fruits, whole grains and fish — may be linked to reduced anxiety, but more research is needed.