My question is: How often are cats in heat? Does it happen once a month? How often?
Janice from the Internet
Actually female cats are almost always in heat or pregnant until they are spayed. While this is a bit of an exaggeration, cats are what are called "spontaneous ovulators" that means they do not release their "eggs" on a set schedule like many other mammals. So a cat will release their 'eggs' whenever she is bred by a male cat, almost ensuring that every breeding will result in kittens.
Cats can reach sexual maturity at about 6 months old, though at this time of year the shorter amount of daylight may delay this in some parts of the country. She will continue to come into heat until she is bred and in the meantime, the crying, pacing and anxiousness will continue as she tries to find a way to get bred. Not a pleasant situation for you or your little kitty.
We HIGHLY recommend that you consider spaying your female kitty as soon as possible, for along with preventing heat cycles and more unwanted kittens, you also greatly reduce her chances for mammary tumors later in life. She also will be a much happier and better companion without the constant drive to find a "man" in her life.