Ah sis, I understand your worry! A positive UPT from a reputable brand like Watsons or Guardian is generally very reliable, but if your period is due tomorrow and you're uncertain, it might be worth retesting in a few days when your hormones are clearer, sometimes timing can affect the result even with a peak OPK. Best to confirm with your doctor though, because they can do a blood test which is the most accurate way to know for sure, and you'll get peace of mind either way.