Unfortunately there is no way to determine pregnancy a day after conception. If you had sex last night and feel that you should know whether you are pregnant or not right away, it is not possible.
It may be the right time to prevent pregnancy as you have 72 hours to take a pill after having sex for negating the chances of conception. There is no pregnancy test which can actually detect symptoms of pregnancy the day after conception. There are a few tests which claim some accuracy but only after 4 to 6 days of conception.
Missing a period
There can be some symptoms of pregnancy after the day of conception but one can hardly rely on them for confirmation. Moreover, a sperm can survive inside the vagina up to 3 days if not more. So, you cannot rely on the night of having sex for any definite confirmations. The first of pregnancy symptoms after conception is missing a period. There is a chance that you confuse implantation bleeding (foetus getting attached to uterus) as light menstrual bleeding. However, check out the darkness of blood. Bloodletting due to implantation is not as dark as the menstrual blood and neither as heavy.
Fatigue is often caused by pregnancy. If you find yourself getting excessively tired for apparent no reason, it may well be due to pregnancy.
Some other symptoms that you can experience by the first two weeks of pregnancy are tender breasts, morning sickness, nausea and vomiting. These symptoms of pregnancy can be experienced even without getting pregnant. It can be quite taxing mentally if you are anxious about getting pregnant but cannot be sure. That is why home pregnancy tests are popular. They can give an indication of positive or negative pregnancy but need to be confirmed by a blood test.
Although there are no recognisable symptoms of pregnancy the day after conception, you can be reasonably assured of it with early pregnancy symptoms. These early symptoms can come as early as the first week to fourth week. Visit a doctor as soon as you feel you are pregnant. It is important that you prepare yourself as early as possible for your baby. It may not be easy to separate pregnancy symptoms after conception from common illnesses and home pregnancy tests do not confirm with certainty. Besides, there are some women who do not show any symptoms at all after even 4 weeks at times.