is it likely i'm pregnant?!?!

i am 16 years old and the last time I had my period was (and this is approximate date, I don't keep track of my period I just have a general idea of when i'm supposed to start, hence me getting this app lol) I believe august 4-th-august 9th. now because I don't keep track of them I don't know too much about their schedule but I do know they are irregular. the last time I had up sex was august 18th. the night of the 19th, technically the 20th because it was passed midnight I woke up in the middle of the night with the worst fever you can imagine, like shaking and trembling and sweating even though i'm cold but my head feels like it's melting type of fever. it lasted like that for a day and a half  almost two days, and then it finally started to wire down to just simple symptoms like headache, and throat ache was a big one, getting a lot of phlegm in my throat as well. anyway all symptoms of sickness went away but besides i still get pretty bad phlegm in my thoat. monday morning I started spotting, and although I feel as if the spotting is getting heavier, at the same time it could just be the fact of the changing of my panty liner time. the spotting started out pink ish red like blood mixed with discharge and 3 days later (today) it's showing up a dark brown. now i'm not sure if my period is supposed to start in a week or 2 weeks, or 3 days, all i know is i've been worrying about being pregnant since i've gotten sick. can you guys please help me out??