Can you feel from inside yourself?

I'm drinking a cold glass of milk and trying to feel it going down. I feel a pain in my belly because of the ibuprofen, I'm hoping the milk will help. I can feel myself swallow, contractions around thick cool liquid in the back of my throat forcing it down into my stomach. I can't feel it after I swallow. I wonder how long it takes it to get down to my stomach?
Nerves inside the body are foreign to me. I don't know jack shit about them. I know when I'm sick but how? What sends the sick signal to my brain? What is the difference between the sensation of touching from the outside and pain on the inside?