Random "drop in chest" feeling. similar to when someone scares you. i am currently under a lot of stress.

Could be stress: Stress can trigger anxiety attacks. People who have anxiety attacks have chest pain, palpitations, shortness of breath, tingling, and a feeling of impending doom. If you think that your symptoms are due to stress, it is very likely true. The attacks can also happen without stress. The attacks usually last 1-2 hours, then improve. If no improvement, see your doctor.