If this just started after your shopping spree, you need to allow time for the refrigerator to catch up with the warmer items you placed in the fridge.That little beep is a warning that your preset temp selection has dropped and needs to be adjusted. Depending on the age of your box, you may either have a loss of freon, or simply a defrost timer/heater problem. To check this, look near the thermostat (temperature adjustment) and find a hole about the size of your pinky finger tip. If you have found the right hole, you will be able to spin your finger around a bit and hear a sound similar to a wind up clock. You may also use a small nail file, which, while it isn't exactly the right tool for the Job, will work quite well for an emergency. Spin this pin around until you hear a click. Be careful not to spin past the click or you will have to spin again (this is the defrost timer). If you were successful, the fridge turned off and has moved into defrost mode. Now you can move to the freezer compartment and place your hand at the inside back wall and feel top to bottom for heat. If there is heat then your defrost heater is working properly. If not, then you have diagnosed your problem to some degree. Three factors play a part in the defrost cycle.
The Timer, heater rod, and defrost limit switch.
At the very least you will be able to point your repair man in the right direction. A quick test for your defrost timer is to mark the point just before if clicks to defrost and turn your timer there, then wait to see if it moves to defrost under it's own power.
Remember, a faulty defrost circuit will cause your freezer to clog with ICE, and no air will circulate.
Also check your refrigerator area to be sure your thermostat rod has not become dislodged (if it is visible).