Can I lose 70 pounds in four to six months?

yes its possible. but you need MAJOR dedication. the running part sounds good. but you need to use more weights to build MUSCLES. when you squats you need some kind of weight because not only are you using your body weight but another source of weight. definitly get on the eliptical,increase the intensity/resistance this way you're pushing your self EVEN more. theres a few workout out tips online. its really hard to explain things that would help work certain parts of your body but you need Cardio .. good luck :)