Emergency spay for dog who may be pregnant?

I called my Vet like almost 2 weeks ago I left a message and thinking that their busy, they have yet to call me back! How much does something like that cost... I live by Philly so I'd like to take her to the Women's Humane Society? How safe is it for my dog? She would be around 3 weeks if she is. I keep thinking her look slightly longer... but I could just be thinking that. She is a small/ medium size fluffy dog and I think she looks fuller, but maybe it's the hair growing in. I'd hate for her to have puppies, so what else can I do. I can't just sit a wait anymore. I gotta talk to someone cuz the further she goes pregnant (if she is) the worse it will be. Is there anything else I can do other then emergency spay? Any information would be great! Thank you very much for the incite!