Except that in chickens, its more frequent than once a month. Egg-laying chickens may produce (in their prime) up to an egg every 2 days or so - there are methods to “trick” chickens into thinking more time has passed than it really has. Chickens are very photodependent in their egg-laying, and so changing ambient light conditions on a regular schedule (8hours on, 8 hours off, 8 hours on, etc) makes their bodies think that that its time to lay an egg sooner than they would in the wild.
And yes, the large majority of the eggs we consume are not fertilized. The exception is the occasional egg produced in free-range conditions, where there is often a rooster for every 10-20 chickens (I don’t remember the ratio for sure - the rooster also contrbutes an “incentive” to lay eggs more frequently). Occasionally, an egg will be fertilised, however eggs are collected every day, and so it does not get incubated properly right away. This also causes the egg to never develop, since it needs to be maintained at specific temperatures throughout the foetal development.
If you’re interested, you can actually examine your eggs to see if they’ve been fertilised, except that the only way to tell is to break the shell (in which case it doesn’t really matter anymore, does it? :)). Break the shell, and examine the yolk. If it has a small, ring-like structure on it (maybe a half-centimeter in diameter) then it’s been fertilised. If it doesn’t, then it hasn’t. Again, this will only happen if your eggs are collected from free-range farms - battery cages don’t have roosters present.
NOTE: IANAChicken Farmer -I took a single course on animal production systems, and spent a very interesting field trip at a government funded chicken farm (as well as beef and dairy farms on other days). I just remember this from that course, so someone else might know more than I do