There are no sure fire indicators without taking your dog to the vet. False pregnancies are also possible where the dog will appear to be pregnant.
English bulldogs have become one of the most popular breed of dogs on the market today. They were first bred with a fierce fighting nature, but since dog fighting became illegal in the United Kingdom the English bulldog's fighting nature was bred out of them. This loyal, loving disposition makes them great family pets as well as excellent show dogs. If you have opted to breed your dog, recognizing signs of pregnancy is not a substitute for examination and follow-up by a reproductive veterinarian.
Make sure she was ovulating. Due to hormone changes, when the bulldog is heat, the bulldog may show signs that she is ready to be mounted before she begins to ovulate. A surefire clue of ovulation is when she starts showing visual signs of being in heat (i.e. bleeding). It is very improbable that your bulldog will be pregnant if you attempted to mate her even just a couple of days before bleeding.
Check the food bowl. If she is not eating the food in her bowl, this may be an indicator that she is pregnant. An initial decrease in appetite is a common indicator that the dog may be pregnant.
Try and play. Sluggish behavior in your dog is an indicator that she might be pregnant.
Roll her over and look at the nipples. If her nipples have grown that is another indication that she might be pregnant.
Look at the belly. A later indicator is that dogs will quickly begin to show growth in the abdomen. Most dogs have a pregnancy period of anywhere from 54 to 72 days with an average of 62. Therefore, you will see growth in the abdomen after the first couple of weeks.
Take her to the vet. The vet will be able to tell if your English bulldog is pregnant. Most vets can determine pregnancy just by feeling the abdomen of the dog within the first 20 to 30 days after conception. An ultrasound is also possible. At around day 25 the vet will be able to hear fetal heart beats. In some cases the vet may use X-rays to determine whether little puppies are on the way.