Background: I am starting to breed ball pythons when i had to move to Oklahoma (military move) the price for rats out here is crazy like $5 for 1 med. so i decided to start breeding rats. I kept my extra feeders (the ones my snakes did not eat) two females were in a glass aquarium with one male (if i sexed them right) until I could get the rack built when I took the male out to feed my snakes I noticed my female had gained a lot of weight after a couple of day she has gained more. and now she is very aggressive.

Questions: is my Rat pregnant? how do I tell if she is Pregnant?
Thank you for all your help!!!