The signs vary from woman to woman. But most women claim to just "feel pregnant". Some signs might be cramping, a brown or reddish tinted discharge, feeling tired, nausea. Unfortunately there is really not an absolute sign to tell if you're pregnant without taking a pregnancy test.
Ativan is FDA pregnancy category D which means it can cause birth defects in an unborn baby. Do not use Ativan without your doctor's consent if you are pregnant and tell your doctor if you become pregnant during treatment.
You can't tell for sure without taking to a vet. A lot of dogs display false pregnancy symptoms. I hear they can do a test, but the best way is to wait until 21 days in and get an ultrasound. It will also tell you how many you are expecting.