pls reply me, normally my mensuration used to last for 5days with heavy flow at least the first three days will heavy and last two days will light, but for the past two months now my mensuration has change to 3days and the worst part of it is that it is the only first day that will heavy, the second day will light and third day will lighter, and it wasn't like this before i started having sex. can sex cause this or am i pregnant?