###Human: I am sexually active and period is delayed though UPT is negative. Kindly help. ###Assistant: Hello. If condoms are used correctly, they are about 80 % effective in preventing pregnancy. Stress and illness and taking certain new medications can definitely affect when your period comes. Have you had any early symptoms of pregnancy which most girls experience before they even have a positive pregnancy test? If you need accurate confirmation of pregnancy as soon as possible, you can have blood work done that I recommend for patients in your situation. Also, finding a different contraceptive option that is right for you can help in the future. Just let me know what your preferences are and I could help if you would like to explore birth control options.