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It is not possible (except in rare cases) to secrete pregnancy hormone HCG (which is responsible for the positive UPT test), without being pregnant. The stress of infection, emotional and personal issues can delay your periods but they will not cause you to have positive pregnancy test.
In rare cases, UPT can show false positive results that include: use of medications that could resemble the hormone molecule, use of infertility drugs, liver disease, liver cancers, choriocarcinoma, germ cell tumors, IgA deficiencies, gestational trophoblastic disease or neoplasm, presence of heterophile antibodies etc.
Consider visiting a gynecologist for further discussion and evaluation. The chances of pregnancy cannot be ruled out (pull out method is associated with highest failure rates). If pregnancy is suspected, a serum/blood HCG test should be done to confirm/rule out pregnancy accurately.
Take care.