If you've been checked and cleared for any possible heart problems, then the other most likely causes are Acid Reflux/Indigestion (the pain is commonly mistaken for heart problems, and is very strong), or muscle / ligament damage in the rib or sternum area where the pain is.
If it's happening on a monthly basis, I'd track what you eat - keep a log when it happens to see if you can equate it to a specific food (anything spicy or acidic will do it) or a class of food. Having had Reflux for years, I know the pain you're describing, and it is not fun to deal with. It comes in waves and can last for a long time.
If you haven't been checked for a heart problem then you should. A cardiologist can give you a portable chest monitor to wear, or they can determine if you have a problem in their office by running an EKG. Reflux is one thing, but heart problems must be caught early in order to be dealt with effectively, so at least get it checked so you can rule it out if nothing else.
If something happens twice a month it is called biweekly because it happens every other week and a month has 4 weeks. there is also bimonthly which is every other month but not really a direct word for something that happens twice a month.
He gets to pinch and punch for the first of the month against his friends. Seriously, nothing happens to every boy every month. There is no equivalent of the female menstrual cycle or any other event specific to males on a monthly basis. and he masturbates every month
Nominally 2 hours earlier per month.
The letter "e".
They align twice with the Earth.
That month
pay attention to what you are eating.
when you miss your period one month don't be alarmed it happens 2 every one
It depends on hours worked.
A leap year happens every 4 years, where February has 29 days instead of the normal 28.
It happens on the first Saturday of every month. Bezzie Jezzie
you should feed them 2 to 3 every 3 hours