Pregnancy cant be confirmed until 30-35 days, usual signs of pregnancy would be growth of milk sacks, dog would take more rest, compartively less active. Scanning should confirm the pregnancy aftre 40+ days.
These symptoms could also be due to harmonal changes during heat and post heat, they may show all signs of a true pregnancy but it could be psuedo pregnacy (fake pregnacy)...
Food should be royal canine A3 maintenance + 2 eggs + 300 grams of curd till 30 days from mating, after confirmation u can give verol syrup, calcium + 2 eggs + A3 Royal canine till 60 days and later, u can also give beef or chichekn soup well boiled.
Note: My comments are based on 5-6 years of breeding exp, please consult your doctor at every stage for a more specific / customized advise.