If you had unprotected sex, yes, you could be pregnant. You also did not follow the instructions for Yasmin (and that's a very dangerous thing to do). Taking a "handful" of pills following unprotected sex is NOT going to prevent pregnancy.
You need to call the Physician who prescribed the pills, explain what happened and how many pills you have taken.
You have overdosed - the symptoms are as you described (usually a bad headache, vomiting, diarrhea).
You should not be on medication which you do not understand.