Do I need to feed the mother special food or treat her diffe

If you think your piggy is pregnant then keep feeding her on her usual dry piggy mix, make sure she has plenty of hay and keep providing her with her usual 'fresh' food for Vitamin C, you may want to also give your piggy extra Vitamin C (i.e. extra fruit/veggies - but watch her droppings) or in supplementation form (crush part of a Vitamin C tablet over her fresh food). Make sure she gets plenty of exercise and handle her extremely gently - do not pick her up unless you really have to. A healthy diet and exercise can help to prevent pregnancy toxaemia which can be fatal.