A pulsing feeling in the upper abdomen without pain is usually just awareness of your own abdominal aorta, more noticeable with higher body weight, and on its own it isn't typically a sign of
liver trouble. Heavy drinking, even once a month, still adds strain on your liver over time.
Next Steps
A
liver function test and an abdominal ultrasound would be worth doing, especially given your weight and drinking pattern. Cutting down on the amount each time you drink will help as well.
Health Tips
See a physician soon if you notice yellowing of your eyes or skin, dark urine, or pain develops.