Whenever i try to exercise i start get tired quickly, i run out of breath, headache and nausea ?

Nauseaw/exercise: May just be deconditioning -go slowly start 5-10 minutes a 3 x a day walking or may be reflux -try Mylanta or famotidine or related to thyroids ( check thyroid) or related to heart/lungs. Would go for exam to evaluation and get EKG, pulmonary function testing, basic blood work . if still persists may need additional imaging. Would also check mammogram at age 45.