I tried moving but it hurt so bad to even try to sit up. I was laying down on my stomach with my knees tucked in when the pain started and I couldn't bring myself to to sit up cause it only got worse whenever I tried. My mom told me it shouldn't hurt as bad as I described it when he kicks so I'm a little worried now. I don't know what else it could be!

you could try ice water, juice, walking around.. etc. to try and get him to move

yes, sadly he can kick you anywhere. he could be kicking you or sitting ok n nerves in your back