Diagnosed with bladder infection; 5-6 weeks pregnant; severe abdominal pain and vomiting. should i go back to the er if my symptoms haven't resolved?

Yes, or contact MD: Two possibilities based on your brief description, both of reach require either a call to your doctor or a visit to the ER. 1) you may have a kidney infection (fever/chills, back/flank/abdominal pain, nausea/vomiting) which likely would require a change in your current UTI treatment; or 2) you have an entirely different problem causing your symptoms requiring further evaluation and tests for a dx.