I’m new at this and I need help!!

So I had the Nexplanon since March 2018. I took it out this August 16. I got my period on August 22. So after my period ended I had unprotected sex every single day up until yesterday 9/26. On the day before my period was supposed to come (which was last Friday) , I started spotting very lighly bit it was brown. It was like that until yesterday it stopped. It was barely coming out and brown al along. I’ve been getting very dizzy and feeling lightheaded alot. I also salivate very often which makes me want to spit often. Also I’ve been having alot of headaches. I took 2 pregnacy tests which came out negative. Is it too soon to know? Do ya’ll think im pregnant or is it just side effects of me removing the nexplanon? Please respond to mee.