So frustrated :/

I've been TTC for just a couple months now. Had my mirena removed after 5 years and we are so ready for a baby! (my 4th) I REALLY feel like I'm pregnant and have been testing like crazy. I'm 3 days late and it's still saying not pregnant. I'm about to scream lol I've been using the dollar store tests because of comments from other women stating they do work really well. Should I go ahead and buy one of the name brand tests or just wait and trust this cheap dollar one?