Yes, it's good that you're asking questions. But unfortunately, everyone gave you answers: it's better not to breed. Here are some reasons:
-There's already an overpopulation of pet rabbits
-It's difficult to find homes for baby rabbits, especially because they have such large litters. I see free baby rabbits on craigslist and in the newspaper almost every day and they get re-posted
-It's dangerous for the mother. It's not unusual for there to be complications, especially if the mother is young and/or it's her first litter. These complications can result in the death of the kits and sometimes the mother herself (I've known of several rabbits that died while or right after giving birth).
-If you're breeding rabbits, you can't get them fixed. Unfortunately for your does, this means a very short lifespan. Does that aren't spayed have a very high chance of developing uterine cancer--often by the time they're four. The males don't have as big of a cancer risk but I can tell you right now that intact bucks are NOT pleasant to live with in most cases! They spray like cats, are nearly impossible to litterbox train, and some can be aggressive.
The other problem is that it sounds like you have two rabbits that you don't know the genetic background of. That's never a good idea, who knows what kinds of genes you're passing on to the kits? Responsible breeders don't stick random rabbits together, each breeding is carefully planned out based on genetics. Honestly, poor genetics could be why you lost the kit.
I'm sorry, I know that's not what you want to hear. You seem to like rabbits and probably want to raise babies, right? Have you considered fostering/rescuing a pregnant doe or even one that's nursing? Rescuing rabbits is really rewarding and a lot of fun, too