Please DONT IGNORE PLEASE

Hi there so heres the story:Im am 18 years old about to graduate high school, on may 13 2016 i had sex for the first time around 7:00 pm, my last period was MAY 3-8th SO IM NOT REALLY SURE WHEN I WAS SUPPOSE TO OVULATE which is KILLING ME BUT ANYWAYS im pretty sure he didnt ejaculate inside me Because he only tried to put it in like 2 or 3 times, anyways so the next day bought plan b around 9:00 am (sorry if its tmi) anyways after taking plan b a week later may 19 i had a light/regular period you could say lasted around 4-5 days it was 2 weeks before my expected period, after that i went to the gynecologist 3 days later and explained to her what happened she told me i wasn't pregnant because of the pregnancy test they did which made me feel better but i still think that maybe it was a little too early to know? Ive had had my periods since then meaning i had my period june july and august but my august period only lasted 5 days when it usually lasts 6 days which really worried me so i decided to go ahead and do a pregnancy test which apparently it came back negative? What do you guys think im very paranoid thanks so much for yalls help