It seems that the body protector and the thick jacket were tight enough to compress structures around your chest such as you ribs and the spine. Also movement on the pony must have worsened the pressure on the chest and spine causing trauma. It is seen that such a situation can cause injuries to the ribs or spine and even fractures
. This is what is probably causing difficulty in breathing and tingling
in your legs. You must visit the ER and take Xrays of the painful areas to check if any injuries can be detected. Meanwhile you can take opiod
analgesics depending on your weight and age to reduce pain.
Hope this helps.