boy & girl mice not getting along

Question
i bought two mice a male and female at a  pet store, my original plan was to put the two in a cage together. but it appears to me that they keep fighting, i dont know how mice breed, their positions and such, and i dont know if the reason my female is squeaking loudly is because they are about to be  "doing" it or if its fighting. there is absolutely no blood and i have separated them for over a week since i bought them and tried again a day ago to introduce them again, i dont know what to do i want them to get along and maybe even get to have a litter to care for from them, but i cant differ if theyre fighting or breeding i need help please.
A: how mice act when about to breed
B: how to know when or if to separate them if they are fighting
& C: if this is just normal behavior when introducing them, even though they came from the same cage at the pet store

Answer
Dear Britni,

Two males will usually eventually fight to blood and injury, most especially if there is a female around.  I recommend at least two cages right now.  A male and female will pretty much mate.  It looks a lot like fighting:  The male chases the female around while she squeaks her head off, he eventually catches her, mounts her, biting her ear as she continues to squeak, probably loses her and continues to try until she conceives.  I'd hate to be a female mouse.

Your males should be separated.  They will each need their own cage for life. You should keep one male in with the obviously pregnant (you will know) female *only only only* if you want a second litter of babies, because they mate pretty much immediately after birth.  One more reason not to want to be a female mouse...!  

If they all came from the same cage at the pet store, it's surprising that she isn't already pregnant.  It's unusual for a pet store not to separate the sexes.  It takes 21 days from conception to birth of the pups, so you will know if she came pregnant.

Best of luck and have fun with the babies!  There are plenty of questions about pregnancy, birth, and raising babies in my past answers.  You may also gladly write back.

squeaks n giggles,

Natasha