If you have to keep putting air in one or more of your tires than you most likely have an issue with the tire(s).
It is more often than not your tires valve system. This is the mechanism that sticks out of your tire to allow you to add air. It is probably corroded.
It could be broken or porous and will need to be serviced.
Air loss can be from the rim of the tire at its wheel base. Here, air can escape, causing a slow leak.
Your best bet is to see a mechanic who can quickly fix the air issue and keep you safe on your tires.