pregnant or not?? help pls

it has been 2 weeks and 3 days since the day it happened. happened on august 21st he finished in me (sorry tmi) then again on august 22 then august 23 i took plan b. the pharmacist said it would still work, fast forward 6-7 days later i bled a dark brown slight red color for 3-4 days then it went away, since then im just very paranoid i’ve had headaches every day and nausea every single day. yesterday i took a test that came out negative, but is it possible it could be wrong? i’m just very nervous. then the weirdest thing happened this morning everyday i’ve been nausea after eating but it’s bareable but today while eating breakfast i had to get up and run to the bathroom i gagged probally 20 times before puking up what i just ate, that was the most nausea ive felt. i’m just worried and don’t know what to do my period isn’t suppose to come for like 2 weeks and i i’m scared to wait any longer because i don’t want it to develop body parts or a heart beat:( (im only 17 i know the lecture and how dumb i am please just be nice it feels like my whole worlds crashing down on me) ty