Should I retest later or am I just paranoid?

I have been having what started off as just a casual relationship with my best friend’s older brother for about 3 months. We haven’t told her anything because we didn’t think it would really good anywhere.

However, for the last month or so I’ve been feeling really nauseous and fatigued. I’ve been getting killer migraines and aversions to certain foods. I even put on a few pounds. They all started around the end of my period last month which was much shorter and very different than what I’m normally used to. My period is supposed to start tomorrow but I haven’t gotten any of my normal symptoms. I decided to take a test today and it came out negative.

Should I take another test just to be sure or is this just me feeling guilty and stressed? Also, should I tell my best friend or keep it under wraps if it ends up being negative? Please help 😩