I'm not trying to come at you like anything, and I certainly apologize if it seemed that way. As many others on here though, I do feel it my responsibility to advise against actions that I feel are irresponsible to animals.
Yes human error happens, but it is our responsibility as pet owners to try and reduce the effect that human error has on the living beings in our charge. So far in the last two posts alone you have a dead and half eaten male because either you didn't realize that they had become aggressive to eachother or you didn't realize he was sick, and you have a female whose life is endangered because she may have been accidentally reimpregnated too soon after her litter. In addition you've said that you regularly leave the male with the female until she actually shows weight gain with pregnancy which goes directly against everything that the breeders I know and trust would advise. That really makes it sound like you're in a little over your head and it has started to effect the safety of your animals. I don't mean that as an insult. There are lots of really good people who love their pets who don't have the resources to run large breeding projects well. I myself have had the opportunity to get into a small rat breeding project and am considering it very slowly and carefully because that comes with huge responsibility.
I'm sorry, but you posted on an open forum for all to give their advice, and I just can not tell you that it's okay that you've endangered the lives of two mice by not monitoring closely enough and that you should continue with your current practices. My advice to you is to either scale down a lot, do some more research, and change some of your practices, or stop breeding all together (which is more than likely the best answer.) As with any other advice, you can do with it what you will, and I wish you and your mice good luck.