Pregnancy test help?

I hope this is the right group as I'm not posting about pregnancy test results.

Me and my partner have recently started trying to concieve our second child. I ovulated earlier in my cycle than normal (day 9 into my cycle), took a test 14dpo - negative, then every other day for the past week. I'm now 21dpo, no period in sight (1 day late, but I'm usually earlier by 1-3 days than Glow predicts) but pain in my breasts, constantly tired beyond normal, lots of discharge and hot flashes that have been consistent for the past week.

Could it be the tests I'm using aren't reliable? I bought them off Ebay in bulk but they came with little instructions - the description of product says midstream early detection tests (red dye), but the only instructions there are say "Dip the strip into the sample up to the max line* and interpret results per the illustratuon". *I've inspected them and they have no max line.

I've tried both using them in my stream and also putting them in a cup for about 10 seconds but both times they're negative. Am I not pregnant and my period is just late, or is there still a chance I'm pregnant and I just got a bad batch of tests? Should I just wait a little longer before spending more money on more tests?