Period 4 days late, negative test 2 days ago?

Hey y'all! I have a question for you. My period was due Friday, so 4 days late today (Tuesday). I took a cheap (dollar) pregnancy test Sunday morning, BFN.

My cycles range from 25-28 days, and Friday would have been day 28. Period is yet to arrive, and no normal symptoms of starting.

Could I have tested too early, should I retest?

Or is it very unlikely I'm pregnant, so shouldn't worry about it?

I have been feeling like total s*** the past 2 days, so unsure if getting a bug, or have a bun in the oven!

I have been having major headaches, sensitive to strong smells, and extreme fatigue for about week now. I did have pains around day CD 16 (normally ovulate around CD 11-12) but I assumed was just gas pains.

Do y'all think I'm overreacting, or need to retest ASAP?

Just looking for some opinions before going out to buy test tomorrow?