Are you getting *more* overdrawn? or was there one really bad month that set you back? If you are getting steadily more overdrawn then you need to reduce your mortgage payments, if you aren't then you don't really.

If you do choose to reduce payments now, try to go for something that will let you overpay without penalty the difference between current payments and new payments so that if (when!) your financial circumstances improve you can pay off faster again without going through the pain of remortgaging.