Conception takes place when an egg is being fertilized by a healthy sperm. For conception to occur, ovulation must have taken place. Ovulation happens when one of the ovaries releases an healthy egg which travels down through one of the fallopian tubes. A sperm fertilizes it and then conception takes place. If you are trying to conceive—it is important you know your monthly circle, so as to know the right time to have unprotected sex.
When the egg gets fertilized, it travels down to the uterus and implants itself. Just because an egg is fertilized doesn't mean pregnancy will take place. Sometimes an embryo implants itself in the fallopian tube, this is called an ectopic pregnancy. Ectopic pregnancies are very dangerous if not quickly detected because it can cause a ruptured fallopian tube. If the egg or sperm isn't of good quality, there won't be implantation—hence no pregnancy. A woman isn't pregnant until implantation has happened.
If implantation happens, pregnancy has occurred and the zygote cells begins to divide , and the zygote becomes am embryo. After eight weeks, the embryo becomes a fetus. An accurate way to tell if you are pregnant is by having a test done. Your body might start showing symptoms of pregnancy early. Symptoms like nausea, fatigue, skipped period, implantation bleeding. It is advisable you get a pregnancy test done just to be sure.