4 month old sleeping time

At 4 months, babies do sleep a lot, but 20+ hours a day is on the higher end and worth paying attention to, especially if she seems hard to rouse for feeds or is not feeding well. It could be nothing, but it might also be worth bringing her to the PD just to rule out anything, since at this age good feeding and weight gain matter quite a bit. Better to get a professional to assess and have peace of mind than to wonder.