Kidney infection and pregnancy?

I am about 22 weeks pregnant and for the past couple of weeks I have had some dull pain in my right side around my kidney area. It always hurts, hurts worst at night, but I haven't had any other severe reoccurring symptoms. I have been drinking water and clear fluids to help flush out a possible kidney stone but still nothing. The other night I was feverish and had chills but it went away after I broke my fever. I have been taking tylonel for the pain but I really don't like taking medication while I'm pregnant even though tylonel is approved. I would rather just know what it is that is causing the pain. I went to the ER also about 4 nights ago and they did urine and blood tests that came out normal to show no infections for UTIs or anything so I was sent home, but I'm wondering if I should go back? I'm thinking I have detected an early kidney infection and I should go to the doctor to get it treated but I want to make sure I'm just not having normal pregnancy back pain. PLEASE HELP!!! Its 4am and I haven't slept through the night in days!!! Oh I also read that nocturia is a symptom and that I have had but I figured thats because I can't sleep because of the pain and I wake up.