For me, the extreme fatigue and sore breasts started exactly around week 5, right after my missed period. It varies a lot, some of my friends didn't feel anything until week 8.
Don't waste money buying early testing kits as they can give false negatives. Wait till your period is late by at least 5-7 days, then test; it saves extra doctor and lab visit expenses.
While minor changes happen earlier, noticeable symptoms usually peak around week 6 to 8. The most reliable way to confirm is a blood test or consulting your doctor rather than waiting for symptoms.
Don't worry yourself looking for symptoms every morning, beta. Stay calm, eat healthy, and test only after your period is missed; everything will happen beautifully.
I have been tracking my cycle very carefully too. I read that some women get mild cramps during implantation, but typical symptoms like nausea mostly start after the 6th week.