I Went To Urgent Care Yesterday Morning And Was Diagnosed

I went to urgent care yesterday morning and
was diagnosed with an UTI and kidney infection. I was placed on nitrofurantoin mono/Mac and have taken 3 doses so far. The pain in the lower right side of my back is getting worse, and I cannot find a comfortable way to sit down due to it. I would rate the pain an 8/9. The doctor at urgent care said that if my symptoms worsen I should go to the emergency room, however I do not want to go unless if it is really needed. Should I go get checked out at the ER due to the increase in kidney pain? Thank you