I inhaled some food 8 days ago i feel out of breath after eating only would i know if i had aspiration pneumonia ?

Unlikely but see Dr.: If you have a normal cough reflex you likely expelled the particles as they entered your trachea. If the particles reached your lung contaminated with bacteria and developed into pneumonia you would usually have cough, fever and shortness of breath and feel ill. These symptoms might develop slowly over several days or weeks in some cases depending on the type of bacteria. See your physician.