PLEASE HELP ME, SCARED

so i am 15 years old and lost my virginity june 27th , i am on the pill and he pulled out. i was having so much stress and anxiety about possible pregnancy that i became very sick. i went to the doctor a week later and got a blood pregnancy test , results were negative. then i started my period that day and have had bad cramps and a medium flow for 3 days (period was a week early) . do i still have a chance of being pregnant? (i read some things that say you can think you have your period but it’s not) i really need help please respond