If left to their own devices queens will have 3 or 4 litters a year, until they end up in such bad shape from losing condition and weight from feeding the babies that they can't conceive any more, and this often shortens their life very significantly. The reason for this is that giving birth causes a season within 3 weeks of the birth. It's really not recommended though.
Cats in the wild have lots of babies in order that some survive when lots of them die- but whereas in the wild if they have a litter of 6 only a couple will survive to adulthood (therefore the calorie drain on the queen's body is lower), in house cats all 6 are likely to survive. A queen feeding a litter of 5 will be using 4 times the calories that they would need if they weren't feeding.
I really would like to question why you're putting your cat through this at all? Unless you're breeding pedigree cats (in which case you shouldn't be letting her have more than one litter a year and should have learned about this before entering into it all anyway), there are too many unwanted kittens in the world for me to support anyone adding to the problem.
We have too many unwanted kittens through the Shelter.
We have too many knackered queens that have had litter after litter until they look old when they're 2 years old.
There is a really simple operation that would stop this happening, and would stop the dreadful levels of Feline Leukaemia Virus and Feline Aids (both sexually transmitted and both of which you really need your queen testing for)- get her spayed and let her have a nice life that doesn't include being a baby machine.
I'm sorry if I don't seem very supportive of you in this instance, but if you want to see the results of people letting their cats have kittens without thinking about the consequences come and visit the Shelter one day- we're too full to help anybody except those in the most dire of situations at the moment.
Insecurities are about as useful as putting the pin back in the grenade.