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Since you did not have unprotected intercourse and if condom was intact chances of pregnancy are not possible.The white stain on the sheet could be your vaginal discharge which would have been secreted or precum of your partner which would have spilled on the cover.
Wait for the periods and do not take stress as it can delay them.If the periods do not start even after a week of expected date consider visiting a Gynaecologist for evaluation.
Take Care!