It's may be due to 2 reasons 1. Ur feeling breathing difficulty U take more inspiration expiration by using chest and abdominal muscles so more work on those muscles U feel pain in chest and ur heart rate also increases
2nd reason due to anxiety or stress and panic
Next Steps
for reason 1 U closely monitor spo2, take ecg for chest pain
if any breathing difficulty U consult doctor
for reason 2 don't be panic ,take good diet sleep well avoid stress and anxiety