How do you overcome a plateu without changing your diet and exercise plan???

The only way to overcome a plateau is patience and switching it up. Sometime your body just reaches a point where it can't loose any more at that time. Give it some time. And also, you really should switch up your workout. I know you said you like what you're doing, but it's probably not enough of a challenge for you any more. Try going for a jog/run, or head to a gym, if you can afford it. There's a great variety at most gyms to give you new things to try that would challenge your body in new ways. Also, make sure you're getting enough protein - very important to make sure your body doesn't break down your muscels for fuel!