There are signs and symptoms but the only way to be sure is with a test at your doctor or clinic. Some signs are no period, tenderness in your breasts, weight gain. If you think you may be pregnant go to your doctor or clinic right away.
The only definite way to confirm if you are pregnant or not is by taking the test. This is because the first symptoms of pregnancy differ from one woman to another and also from pregnancy to pregnancy. You can find out more information here http://www.webmd.com/baby/guide/pregnancy-am-i-pregnant.