Could i keep my braces on couple more months if its time to take them off because i want them on little longer ?

Time: Time in braces is determined by treatment result, not by the calendar. Braces should be on only long enough to provide the best treatment result possible, no longer or no shorter. Please discuss this with your dentist or, hopefully, orthodontic specialist.

Why?: Why do you want them on longer? If it's because you are not happy with the end result, let the orthodontist know that ; see if there can be any other improvement in line with your desire. If it is not possible to improve upon what you have now, leaving them on longer will not only not get you the result you want, but will increase your chances for decay and decalcification and perhaps cost u more!