Salam,dr.sahib!in my humble opinion you should complete your M.B.B.S and then attempt css exam.For ce is usually held in february and profs in december,january.So you will not be able to cope with the exams as required and i fear,repercussions will be undesired.because you will always relegate css to profs ,consciously as well as subconsciously.Inshallah,iam to going attempt ce 2013 as my house job was completed in june 2012.I hope of conveying my opinion.
Regards