My two pit bulls

[Rebekah12]

i have a 4 year old female pit bull thats in heat and a 2 year male pit bull they have been locking up about 6 to 8 times a day but when he dismounts her she pushes everything out of her how will i know if she is pregnant or even if she can get pregnant ? or is that natural for her to do that some one any one please help with this i really want them to have puppies