The most you can do is check your air filter and your evaporator coil, (if it is at the bottom of the air handler)... If neither of them are clogged up and coil is not frozen, then it is time to call in ac technician to have it inspected..

Limited info but maybe frozen coil or loose belt???

Maintenance. Check air filter, clogged air flow thru evaporator, cracked buildup in indoor fan fins, fan speed, oil fan motor. Inspect duct work.

Check for disconnected duct work.