What Causes Delay In Period Despite Having Nordette Post Non Penetrative Sex?

She had her last period on Feb 14. We tried to do the deed last Feb 28 at 11:30 am but i just rubbed it against her vagina. I m not sure if precum came out and then we stopped. She found out later that evening that she was ovulating so she drank 4 pcs of nordette after 46 hours and the next dose after 12 hours last Mar 2. She is experiencing sore breasts and cramps but still no period until today. Is she pregnant? We re so worried. Please help. We saw that precum can get you pregnant.