Could I be pregnant after six days of taking the pill?

Patient: I started taking Cerazette about 5 weeks ago, mid cycle but had intercourse, he pulled out, 6 days after I started taking it. 4 days later I had what I think was a period, it started with a brown discharge they on day 2 was red brown blood. The period lasted 5 days and i had period pains. Now 25 days after the sex im having some pregnancy symptoms – light headed, lower abdominal cramps, sore breasts, slight nausea but I’ve done 2 test which were both negative. Could i be pregnant?