T.R.
Because you say you've never felt this way before & it sounds like significant pain, I urge you to go to ED/Urgent Care & get screened for possible kidney stone or appendicitis. Both have similar symptoms & both are potential emergencies (kidney stone if they do s it is blocking the function of the kidneys). Hopefully they will check you out & say all is well you have a stomach bug, but if you were my daughter/sister, I would insist you get evaluated now.
Good luck & please let us know you are ok.