Axolotl females don't become 'pregnant' in the same way as other animals. Mature females are always full of eggs, hence their 'rounded' appearance and egg shape. If you have seen spermatophores around the tank (they look like mini versions of the curly hill in 'A Nightmare Before Christmas' if you're wondering), and the female begins laying eggs, then your female has become 'pregnant.' As far as I know females don't hold the eggs in their bodies; fertilisation happens internally, and the female lays soon after.
My female laid one day after we found spermatophores in the tank. I had removed one of my males because he had injured himself and the other male decided to take a chance >.<