What the cause of tightness in my chest and lower back pain?

You look young: And that usually means a strain of muscles and ribs in the chest and spine muscle in the back. The chest could be asthma or unlikely a heart issue. Lung functions and a possible "regular" stress test can also help, but seeing your dr will help sort this out. Physical therapy and yoga will likely help both.

CP: Chest pain causes: heart attack, musculoskeletal pan, coronary artery disease, aneurysm, pulmonary embolism, esophagitis, acid reflux, pneumonia, gall baldder disease etc. Get checked with your doctor if you have persistent pain.