28 days late need help !

28 days late negative tests so far, all of them were cheap tests, any ideas ? Should I get a more Senstive test ? Or Iv heared soem people being like 7 weeks pregnant and it didn't show till then. According to glow/<a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> I should be on the second day of my period but I didn't even start the last one yet... need help !