im bleeding and i really dont know why? I'm too young to have kids

this is what happened to me ...I HAD MY PERIOD 13 DAYS AGO.. i had sex last week and i went to the doctor for s plan b and after that everything was very good, no pain no bleed or nothing. the following week, exactly 7 day i had sex again yesterday  and my boy cum inside by accident so for then i was ready to get the plan be one more time to prevent pregnancy at all. im 17 and i still in high school. i felt to sleep and two hours after i star a light bleeding ... the same night i dint sleep with horrible cramps and i woke up to go to the bathroom and i was bleeeding the day after (today) y still bleeding and having little cramps.... im SOO WORRY AND SOO CONFUSE I DONT KNOW WHAT TO DOO...HOPEFULLY IM NOT SICK OR NOTHING , I WILL GO THE DOCTOR TOMOROW FOR ANOTHER PLAN B PILL FOR THE LAST TIME IN MY LIFE, im soo dissapointed with this...but i will like the hear some opinioN thaT could relax me...PLEASE HELP ME IM JUST 17 THANKS.. :'(