My period only lasted two days instead of five. could i be pregnant?

No: If you had a period than it is very highly unlikely that you are pregnant. However, you can obtain a home pregnancy test if you are concerned about pregnancy

Probably not: The fact that you had a period, although it was shorter than usual, makes it unlikely that you are pregnant. Most women have an usual period (shorter, longer, lighter, heavier) once in a while and it is not usually reason for concern. If you have had unprotected sex within the past month, it is probably a good idea to do a pregnancy test.