If I’m 15 days late on my period and 3 positive pregnancy tests is this 100% pregnant? ?

I’ve done 3 tests but I don’t believe them because they’re from the dollar store? They all said positive but I also haven’t had a period in 16 days and have been feeling nauseous. Are cheaper pregnancy tests accurate too?

If I’m 15 days late on my period and 3 positive pregnancy tests is this 100% pregnant? ?
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