Look at the "Pregnancy Monitor" on your chart. There are some signs that can give you some clues. If your temperature stays elevated past your usual luteal phase length, that is a good indication that you could be pregnant, if you had intercourse within your fertile time and if ovulation is clearly visible on your chart. By this time, you are usually able to get a reliable result on a pregnancy test. The pregnancy test is really the only certain confirmation that you are pregnant.
Some women notice other signs before a pregnancy test can be taken (spotting, higher temperatures, breast tenderness, frequent urination, nausea, "feel pregnant"). However, these and other potential early pregnancy symptoms can be experienced with or without pregnancy. Because you can be pregnant with or without these symptoms, they cannot tell you whether or not you are pregnant.