I want to replace a breaker with a bigger (higher capacity) breaker...

Do not do this! The reason your breaker is tripping is exactly what it was designed for. A tripping breaker ids telling you to the circuit is overloaded or the breaker is worn out and needs replaced with the same size and type of as the original. Besides dedicated circuits, your multi-wire branch circuit is designed to power multiple devices, lights and fans. If you turn all of your items on and the breaker trips, you probably overloaded the circuit.

Replacing the existing breaker with a higher capacity/size simply exposes your circuit to a heat/fire hazard. The best fix is to limit the number of electric devices you use on a given circuit to avoid tripping the breaker or have an additional circuit installed by a licensed electrical contractor to provide you the proper power requirement for your needs. If a breaker continuously trips and you feel you are not overloading the circuit, contact a licensed electrical contractor to assess the condition of the breaker and circuit.

The US Consumer Products Safety Commission issued the following recommendation: "Investigate to determine why a fuse blows or circuit breaker trips. Do not simply replace the fuse or reset the breaker. If a fuse blows or breaker trips, it is often a warning that the circuit is overloaded. Check the circuit for causes of overloading (for example, too many appliances plugged in, a malfunctioning product, a short circuit). When in doubt, consult a licensed electrician."