Chat history from one to another phone


Since today I have a new phone, and happy as I was, I was installing whatsapp asap. I skipped the part of using any back up, but now I see, that seems to be the one and only time I could get the back up. I already tried reinstalling the app, but it automatically uses the phone number which I verificated the first time. Is it possible to get my chat history back, or is it really gone?