Negative tests but symptoms

I’m 18 days late . Took an FRER yesterday middle of the day , negative . Yesterday felt nauseous and light headed . Today woke up at 4 am to puke my guts up . I’ve been moody and emotional . If I was pregnant by my period I would be almost 7 weeks . Which is about the time I had morning sickness when I was pregnant . What is wrong with me ?! What’s the chances of me being one of those people who doesn’t get a positive test until I’m farther along ? My mom didn’t get a positive on a test until she was 3 or 4 months with one of her pregnancies .