Why do I feel the need to take excessive deep breaths? It causes me to get light left side back pain n light chest pain & lightheadecan it be anxiety?

Yes, it can. Anxiety can involve mental, emotional, and physical symptoms. These commonly appear in respiratory system as well as cardiovascular, gi, and neurological systems too. For thoroughness it's a good idea to have a checkup with your primary care doctor. But your anxiety can be treated with a combination of psychotherapy and medications if those are needed. A psychiatrist & psychologist can help.
Could be. You have multiple symptoms, before labeling it as anxiety, go to your doctor make sure you do not have anything else.