I am 20 years old ,my periods were normal till

Patient: I am 20 years old ,my periods were normal till last month. But this month i am 13 days late as i took a contraceptic pill last month to avoid pregnancy and my hpt was negative i checked it 3 times. Yesterday my periods were started with a peice of flesh like something coming out with a heavy pain and yesterday night it was my stomach was paining so i took a medicine which my doctor have suggested to take in those days to avoid pain. Today morning i woke up with no signs of periods which makes me too much worried. I cant tell to anyone as i am sexually active and my parents are not aware of this. So So need a suggestion what are the possibilities, Please help me i am really worried…

Doctor: