A "true" plateau is when your bodyfat % drops to very low percentage and your fat loss stalls in excess of 3 weeks...
At 263 you should dropping at least 1-2 lbs each week. That said, I would HIGHLY recommend you monitoring closely your daily calorie intake. Weight/fat loss is ALL about diet, exercise is only 10 % of that equation.
It is possible that you could not be eating enough...or too much.
If you post a typical days meals/calories, I think you will find that the recommendations you will get will be more tailored to your "specific" needs.