How long have you had her? Gestation period is usually 63 days in dogs. If you haven't had her that long, she could be pregnant and you may not even know it.
I also have a female that had a "false pregnancy" with her first heat cycle. She gained weight, produced milk, went through "labor" and all of that. We were so scared our beautiful pitbull locked up with something, but she never had puppies. Her next few heat cycles it didn't happen. When we actually did breed her, we were kind of worried that it would be the false thing again as everything symptom wise was the same as the false pregnancy, but she delivered 13 puppies that time.
Hopefully it is false, but if it isn't, don't freak out! We're here to help! You may want to make a whelping box for her just in case and get everything ready. You don't want any unexpected surprises on your bed or couch! LOL! Keep us posted and let me know if you have any questions or need anything. I'm here!