Since you have swollen throat, pressure in kidney areas while urinating, and low back ache, the first thing to be rule out is streptococcal
infection. These bacteria can affect both
throat and kidney at the same time (though usually kidney is affected 1-2 weeks later) and if left untreated can be dangerous. Please consult a doctor immediately. You need a throat swab and urine examination and maybe culture of the urine to start with. Take care!