Pregnant Boxer? - Page 1

I bred my Boxer one month ago, and I am having the hardest time telling if she is pregnant or not. Last time I bred her, she showed all the signs of pregnancy and then no puppies. The belly swelled, her mammary glands swelled and produced, she nested, had mood swings, very clingy; then two weeks before she was due she went back down to normal size and nothing. I figured it was the male because another dog he bred to did the same thing. I used a different stud this time, but I'm not too sure on what's going on. I use to breed small breeds, and after getting a Boxer, I knew this was the only breed I wanted to share with the rest of the world! lol. She is showing signs of being clingy, swelling of the mammary glands and producing a tiny bit right now. She knows what the word "puppies" means and she goes crazy everytime she hears it lately. But my concern is that her stomach isn't swelling yet. On average, how far along do Boxers have to be before they really start to show? Small dogs show around 6 weeks at the latest, but I'm not sure with the bigger breeds. She is four weeks along right now. Any information would be great. I've tried doing some research, but none of it is from personal and hands on experience. Any ideas?