Today my whole house main breaker circuit tripped. I went and reset it. After 5 minutes it tripped again. I have my pool equipment and a/c running. I decided to reset it but this time I turn off the a/c breaker. Everything is working fine until I turn the a/c breaker backed on. It tripped again after 5 minutes. I then reset the main breaker. This time I turn off the pool pump and run one of the a/c. No trip from the main breaker. Could my main breaker went bad. BTW it's a 150 Square D.

More than likely it is a bad connection somewhere at or near the breaker. This is NOT something you should mess with yourself. An electrician would need to have the power company cut the power to replace the breaker if that is what is needed.

Call someone ASAP!

Can I shut off the main breaker to check for bad connection.

The short answer is no, because the main breaker is always powered.

The long answer is yes, but it involves measuring the voltage between the cable (not terminal) of where the main power coes in and the panel bus with a sensitive voltmeter capable of measuring in millivolts when under load. This isn't recommended for the novice)

Measuring the temperature of the breaker housing is another way. A finger can work, so can an IR thermometer.

The loose connection can be anywhere. The main panel, breaker, the meter, or the overhead connection.