Because of severe workout muscular pains are common , in your case you have got severe back pain , that's may be due to heavy weight lifting without strengthening your back

hi, good to hear you have opted for physical therapy to reduce your weight, but go slow with the exercise program, your muscles will not be able to take the strain of strenuous exercises, unless they are slowly trained to take the strain. please get a good trainer who understands your requirement, rather than one who follows General exercise regimens, for your pain, please give a gap for a week and begin afresh, local hot fomentation should also help

Hi, I hope you are not in too much of agony. Working out all of sudden without proper instructions or trying to over do something cam cause back pain. I would suggest you consult an Orthopaedic surgeon to make sure everything is alright before you continue with your exercise routine