Do these symptoms, which include chest tightness and a lack of desire to eat after performing Salat al-Istikhara, indicate that I should not proceed with the engagement? And what should I do?

Scholars differ on the reliance of the servant after performing Istikharah: some say it is based on the openness of the heart and the facilitation of the matter, while others say it is based on proceeding with the matter unless Allah turns one away from it. The more correct view is to proceed with the matter after Istikharah, unless Allah turns one away from it. Based on this, we advise relying on Allah and proceeding with the marriage proposal if the girl is outwardly righteous and acceptable, while being diligent in frequent remembrance [of Allah] and supplication.