Please don't leave the site. You just have to understand, this type of question gets asked a LOT and it's almost impossible to answer it online in a public forum. There are many factors as to why your two dogs are not doig nwhat you want- too mang to list actually. This is the type of things books are written about.
I recommend going to www.dogwise.com and getting a basic book on the subject. If that doesn't answer your question, then, I'll stick by my original answer of find a mentor to help you. There's no subsititute for in person help here. You are going to need it. Breeding and welping tiny chihuahua puppies is not easy work and complications arise very frequently. Those complications can not be answered online. They are case-by-case specific and typically emergencies.
I'm sorry if oyu are offended that individuals do not aggree or understand why you are planning on doing what you are doing, but it tends to put people guard when told you got a dog just to breed it, you are taking a pupppy, and then the female is going to leave. It sets a tone for things and does make it tough to answer your original question.
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Chelle and the rest of the crew including, but not limited to Kita and Taiko (the shiba inu wrestle maniacs), Adi (reserved and dignified tabby cat), and all 28 reptiles