Cheap test

So I’m 9DPO and I’ve had some cramping last night and again this morning. AF is due in 5 days. I decided to take a cheap dollar tree pt last night and it was neg. this morning I researched the test and it said there not ultra sensitive to HCG therefore they won’t detect until at least missed period. I was not aware of this so if anyone else picked up some of the dollar tree ones there accurate just not for early detection after fertilization. Hope this helps !