30 lbs in 4-5 months isn't completely unheard of, but don't torture yourself to do it. What you want to do is make a life change rather than "diet" in the daily sense of the word and exercise yourself to death. Numerical weight is really misleading anyways. I guarantee if you cut out the junk and exercise like you said, your body will look great in 4 months, but you might even weigh more than you do now because muscle weighs more than fat. Good luck and keep updating your thread if you have any questions for the whole forum