If you are 20, have regular periods, and your menstrual cycle is about 28 days long, the possibility that conception will take place a few days before your period is generally very low. Commonly, the mature egg is released amid the cycle, after ovulation, which lasts only a few days and is not the best time to conceive. Conversely, the length of one's menstrual cycle can be different every time. Some very early symptoms of pregnancy could be the absence of periods, the feeling of sickness, or the soreness of the breasts. If you are experiencing any concerns or if you believe you have any abnormal symptoms, it is ideal to take a pregnancy test to put your mind at ease. Moreover, it is highly recommended that you discuss this with a gynecologist to get personalized advice and support.