Should I take my 5year old to the ER ?

Ok so my 5yr old started running fever Monday afternoon so I took her to urgent care Monday night the dr. did a rapid strep test that was negative but he still sent a 2nd test to the lab and prescribed her an antibiotic. I have been rotating tylenol and motrin and started her on her antibiotics. Last night her fever reached 104.9 so I took her back to urgent care this time this Dr. said that he thinks it might be mano so he drew blood and sent it to the lab, results should be in tomorrow. He also gave her a different antibiotic. So today her fever didnt really go above 102 but now after a cool bath and cold packs her fever is back up to 104. Could there be an underlying problem that the Doctors just arent catching? Should I take her to the ER again its been about an hr since I gave her more tylenol and the fever still has not gone down. I'm not a first time mom that is just freaking out she is our youngest of 4 and we have been through the whole fever thing before with her and the others but none of their fevers have ever lasted this long or seemed this bad. I always say trust your instinct as a parent but I have already been to the urgent care twice should I ask for a blood culture to be done?